WO2001018617A1

WO2001018617A1 - Remote mechanical mirroring using controlled stiffness and actuators (memica)

Info

Publication number: WO2001018617A1
Application number: PCT/US2000/040860
Authority: WO
Inventors: Yoseph Bar-Cohen; Constantinos Mavroidis; Mourad Bouzit; Charles Pfeiffer; Benjamin Dolgin
Original assignee: Rutgers, The State Of University Of New Jersey
Priority date: 1999-09-09
Filing date: 2000-09-11
Publication date: 2001-03-15
Also published as: WO2001018617A9; AU1251101A

Abstract

A haptic interface enables human operators to 'feel' and intuitively mirror the stiffness/forces at remote/virtual sites for the control of robots as human-surrogates. The system provides a haptic interface based upon a novel MEMICA (remote MEchanical MIrroring system using Controlled stiffness and Actuators) device. The integral components of MEMICA include at least one of each of a miniature electrically controlled stiffness (ECS) element and electrically controlled force and stiffness (ECFS) actuator (31). The ECS elements and ECFS actuators (31) mirror actual stiffness and forces at remote/virtual sites using an electrorheological fluid (ERF). Further the ECFS actuators (31) comprise an electromagnetic part that can actively apply forces on a human operator. The ECS elements and ECFS actuators (31) will be placed at selected locations on an instrumented glove, headpiece or other apparatus to mirror the forces of resistance to motion at the corresponding locations at a corresponding robot end-effector. Forces applied at the robot end-effector due to a compliant or rigid environment will be reflected to the user using this ERF device (10).

Description

REMOTE MECHANICAL MIRRORING USING CONTROLLED STIFFNESS AND

ACTUATORS (MEMICA)

This application claims the benefit of U.S. Provisional Application No. 60/153,143, filed September 9, 1999 and entitled "Remote Mechanical Mirroring Using Controlled Stiffness and Actuators".

FIELD OF THE INVENTION: The present invention relates to haptic interfacing mechanisms that enable a human operator to accurately "feel" stiffness and forces at remote or virtual sites. More specifically, the present invention provides electrorheological fluid based force-feedback devices and is directed towards a telerobotic device derived therefrom that provides position and haptic interfaces between a human operator and a remote or virtual object.

BACKGROUND OF THE INVENTION:

For many years, the robotic community has sought to develop robots that can eventually operate autonomously and eliminate the need for human operators. Robotic systems have been implemented to perform important tasks, especially in applications where anthropometrical movement is preferred but human intervention presents inherent risks. Examples of such applications include removal of hazardous waste and decommissioning of nuclear sites. Since these tasks occur in a highly radioactive environment, robotic and other automated systems are required to reduce worker exposure to radiation.

Remote performance of these inherently dangerous tasks, referred to as telepresence, offers an intuitive method that allows a remotely positioned operator to experience the robot's physical "presence" at the remote, or virtual, site. In telepresence, the operator receives sufficient information about the remote robot and the task environment displayed in a sufficiently natural way such that the operator can feel the equivalent stiffness, temperature and vibration of the object that is being remotely or virtually manipulated or actuated. Such a system needs to respond to data from a plurality of virtual or remote sensors at selected points or joints. The mechanical and thermal characteristics of the remote object, including the compliance and reaction forces thereof, need to be intuitively mirrored. Providing thermal feedback can be easily implemented with existing technology, whereas the mechanical feedback using miniature elements is critically lacking.

Haptic Systems

Telepresence requires a human operator to control the action of a remote robot, where there is a master-slave relationship and where the operator's motions are essentially mimicked by the robot (virtual or real). Since many tasks are quite complicated, it would be impractical to program a robot that precisely replicates human movement for predictable and reliable performance. Haptic (i.e. tactile and force) feedback is therefore necessary for a telepresence system where physical constraints such as object rigidity, mass and weight, friction, dynamics, surface characteristics (smoothness or temperature) are mirrored to the human operator from a remote or virtual site.

To address the need for surrogate robots that remotely mirror human action and reaction, the engineering community has started developing haptic feedback systems. At the present time, haptic feedback is a less developed modality of interacting with remote and virtual worlds compared to visual and auditory feedback. Thus, realism suffers especially when remote and virtual tasks involve dexterous manipulation or interaction in visually occluded environments. An example of a force-feedback telepresence system wherein a human operator experiences the forces felt at a remote site on a haptic interface glove having force and stiffness elements integrated therewith as schematically shown in Figure 1. With present actuator technology, it is easier to produce tactile feedback rather than force feedback, and the interface tends to be light and portable. An example of this is evident in a tactile feedback suit that was developed by Begej Co. for NASA JSC. The suit includes arrays of small pneumatic bellows on the arms, chest and abdomen. Even though the mechanical smoothness and slippage of a remote object convey tactile feedback, the suit cannot reproduce rigidity of motion. Thus, tactile feedback alone cannot convey the mechanical compliance, weight or inertia of the virtual object being manipulated.

Force feedback can be produced by both portable and non-portable interfaces. Force feedback joysticks, mice (such as those produced by Cybernet Systems Co., Immersion Corp. and Haptic Technologies) and small robotic arms such as the Phantom™ (a trademark of

SensAble Technologies of Woburn, Massachusetts) are non-portable devices that allow users to feel the geometry, hardness and/or weight of virtual objects. None of these devices tires the user, since the interface weight is supported by a desk to which the device is attached. Yet hand freedom of motion and dexterity are limited since these devices have a much smaller work volume and fewer degrees of freedom than the user's hand. A few portable systems, such as "Force ArmMaster" produced by EXOS Co. under a NASA SBIR task, allow users to move their hands freely. Portable hand masters, however, tend to be heavy (for instance, the Force ArmMaster weighs 22-lb) and thereby produce user fatigue and discomfort in extended simulations.

The CyberGrasp™ (a trademark of Virtual Technologies) is another lightweight, force-reflecting device in the form of an exoskeleton glove that adds resistive force feedback to each finger. The grasp forces are exerted through a network of tendons that are routed to the fingertips via an exoskeleton. The actuators are high-quality DC motors located in a small enclosure on a desktop. The device exerts grasp forces that are roughly perpendicular to the fingertips throughout the range of motion, and forces can be specified individually. Due to the tendon/cable network, the remote reaction forces can be emulated very well, however, it is difficult to reproduce the feeling of "remote stiffness". Furthermore, the operator is "attached" to the desktop with the cable network such that available workspace and portability are very limited. Other disadvantages include the open-loop force control of the glove that results in a compromised accuracy of the representation of the reaction forces. Electrorheological Fluids

Control over a fluid's rheological properties offers the promise of many possibilities for actuation and control of mechanical motion, thereby overcoming the above-described deficiencies. Electrorheological fluids (ERFs) are electroactive fluids that experience dramatic changes in rheological properties, such as viscosity, in the presence of an electric field. The fluids are made from suspensions of an insulating base fluid and particles on the order of one tenth to one hundred microns in size. In the presence of an electric field, the particles, due to an induced dipole moment, will form chains along the field lines (as particularly illustrated in Figure 2). This induced structure changes the ERF's viscosity, yield stress, and other physical properties, allowing the ERF to change consistency from that of a liquid to something that is viscoelastic, such as a gel, with response times to changes in electric fields on the order of milliseconds. The solid-like properties of ERFs in the presence of an electric field can thus be used to transmit forces over a large range.

Applications

A wide variety of applications that would benefit from this type of technology includes, but is not limited to, the following:

1. Simulators - The ability to perform an operation simulation supported by a virtual reality capability is critical to many technology areas. It allows training operators in hazardous and risky tasks as well as developing procedures that emulate reality.

2. Militarv - There is a need for robots that perform complex and delicate tasks at remote sites, where the task is involved with a large number of unknowns for which autonomous operation may not be practical. Examples include field operation as a bomb disabler or a

"telemechanic" that operates in hazardous environments such as a battlefield or nuclear radiation zone, or areas that routinely experience climactic extremes. Entertainment Industry - Virtual Reality entertainment is a growing multi-million dollar industry. At the present time haptic devices are being added to various video games to enhance their interactivity and realism. Current joysticks are limited in the number of degrees of freedom (DoF) that are available. In addition, they can not generate a realistic feeling of virtual compliance. A new class of devices that can be enabled with numerous DoF control and feedback and also easily handle three-dimensional displays and other complex control tasks is therefore desirable.

4. Nuclear Industry: There is a need for accurately performing delicate and dexterous tasks where a human operator manipulates from a distance dangerous nuclear material.

Accurate haptic feedback will greatly enhance his/her ability to safely perform such tasks.

5. Space Robotics - Outer space and extraterrestrial bodies are good examples of environments where telepresence control of surrogate robots is needed. The capability to operate as a surrogate human, which includes telepresence and performance of remote missions, has been recently implemented at NASA Johnson Space Center with the development of the novel space robot called Robonaut, shown in Figure 3. This robot is capable of performing various tasks at remote sites and serves as a robotic astronaut on the International Space Station (see Figures 3A and 3B). Robonaut thereby provides a relatively fast response time and the ability to maneuver through areas too small for the current space station robots. The Robonaut is designed as an anthropomorphic robot, similar in size to a suited EVA astronaut and having robotic arms that are capable of dexterous, human-like maneuvers to ensure safety and mission success. Robonaut was designed so that a human operator who is wearing gloves/suit with sensors can control it. Unfortunately, due to unavailability of force and tactile feedback capability in the control suit/glove, the operator determines the required action by visual feedback, i.e. looking at the Robonaut action at the remote site. This approach is ineffective and consequently limits the potential tasks that Robonaut can perform.

6. Medical Research and Education - Virtual Reality (VR) in medicine is an emerging field of research. Surgical planning, interoperative navigation, simulation of surgical and endovascular procedures for training of doctors, rehabilitative medicine are some of the applications that will be greatly benefited from using the various modalities developed in VR for human-computer interaction. Force and tactile feedback greatly enhances the virtual reality experience, since much of the skill that a medical doctor possesses is in his ability to explore and diagnose by touch. Telepresence technology in medicine is an enhanced form of teleoperation where the medical operator receives sufficient information from the remote robot and the task environment displayed in a sufficiently natural way, that the operator would be able to feel the equivalent of physical presence at the remote site. Some of the areas in medicine where the technology described here can be used are:

Recently there is also an increasing need to improve teaching and training techniques in medicine and more specifically in surgery. This is due to the fact that advances in technology are making medical environment such as the operating room more complex, sophisticated and computerized. In order for the medical personnel to be able to use all new equipment and techniques, modern medical education and training methods need to be introduced. One of the trends in medical education to improve the skills of medical personnel using modern computer based tools, is using computerized models of human anatomy to replace cadaver specimens. A virtual reality surrogate that can be viewed, manipulated, and dissected would be of use for both training of medical students and for the development and refinement of surgical skills for new and existing procedures.

One important concept in Virtual Reality (VR) medical training is user interactivity that allows the user to navigate, understand complex 3D structures and be trained in visuo-spatial tasks. User immersion in virtual environment is achieved with hand tracking devices, motion-coupled head mounted displays and motion-tracking body suits. The haptic (touch, or having to do with touch) and kinesthetic (sensing orientation and position in space) components of the environment complete the interactive experience. These can be provided through tactile and force feedback devices. Haptic interface is necessary in this environment to provide the correct feel for performing manipulation procedures. Current modules for Virtual Reality medical training are limited mainly to visual displays and renderings tied to a description database, which provides information about the object of interest. In cases, where haptic feedback has been introduced, the haptic device used had all the weaknesses of currently available. These weaknesses reduce considerably the level of user immersion and hence reduce the user performance and success of his/her training.

7. Telesurgery

Remote surgery can be enabled to benefit sites that are lacking local medical-care facilities or specialized medical staff. The technology can be used to simulate or remotely perform minimally invasive procedures such as angioplasty and other catheter base procedures. Besides helping rural areas and the military in battlefields, "telesurgery" can benefit future NASA missions. Manned missions are being pushed to new frontiers, at growing distance from earth and are expected to last years. A major obstacle could rise as a result of the inability to perform invasive medical procedures. Surgical robotic systems that are commercially available at this moment do not have a force-feedback modality (see Popolow, 1999).

8. Rehabilitation

There is a need for developing assistive devices for several categories of patients such as patients recovering from surgery or stroke or patients with neuromuscular diseases, such as Parkinson's. Such assistive devices can help monitor the patient's condition and apply force for training and rehabilitation purposes. The technology described herein can operate as an exoskeleton to assist physically impaired individuals who need augmentation of their activity and possibly prevent them from accidental falling.

The conventional systems that have been previously used to meet the above-described robotic applications demonstrate a plethora of limitations. Weak, heavy and voluminous actuators are often incompatible with human anatomy. In addition, a lack of advanced sensory interfaces and the use of conventional control approaches impede interaction between human and artificial members. As a result, current manipulative articulated devices do not offer these capabilities require extensive investments of time and resources that directly increase costs not only due to testing delays but also due to increased difficulty in manufacturing the resulting robotic device. In addition, existing systems cannot accurately mirror the "feeling" of remote/virtual stiffness to the operator.

If the user is to interact in a natural way with the robot, the interface must be intuitive, accurate, responsive and transparent. This requires an interface device that determines an operator's movements without interfering with operator motion or encumbering any part of the operator's body. Furthermore, the operator must be able to extract information about the robot and its environment to effectively control the robot.

It is therefore desirable to utilize ERFs to produce feedback haptic devices that can be controlled in response to remote or virtual stiffness and force conditions. Forces applied at a robot end-effector due to a compliant or rigid environment can be reflected to the user using such an ERF device where a change in the system viscosity is in proportion to the force to be transmitted.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a telerobotic device that more accurately simulates the mobile and sensory capabilities of anthropomorphic movement.

It is further an object of this invention to provide a telerobotic haptic interface that is actuated by an electrorheological fluid.

It is still further an object of this invention to provide a haptic interface that implements sensors to more accurately detect interaction between the wearer and the environment.

It is still further an object of the present invention to improve the lifting capabilities of telerobotic devices. It is still further an object of the present invention to improve the interactive mobile and sensory capabilities of telerobotic devices and human operators in the form of an exoskelton.

It is even further an object of the present invention to provide the ability to change the viscosity of an electrorheological fluid by electrical stimulation, thereby allowing for the construction of devices with controlled stiffness and force feedback.

It is yet further an object of the invention to provide a hybrid actuator using an electrorheological fluid and electromagnetic cylinder.

In the efficient attainment of these and other objects, the present invention provides a haptic interface based upon a novel MEMICA (remote MEchanical Mirroring system using Controlled stiffness and Actuators) device. The integral components of MEMICA include at least one each of a miniature electrically controlled stiffness (ECS) element and an electrically controlled force and stiffness (ECFS) actuator. The ECS element mirrors actual stiffness at remote/virtual sites, using an electrorheological fluid (ERF). The ECS and ECFS elements will be placed at selected locations on an instrumented glove, headpiece or other apparatus to mirror the forces of resistance to motion at corresponding locations on a corresponding robot end-effector. Forces applied at the robot end-effector due to a compliant or rigid environment will be reflected to the user using this ERF device where a change in the system viscosity will occur proportionally to the force to be transmitted.

In a preferred embodiment of the present invention, the MEMICA is a haptic interface system that may be used to construct a glove equipped with a series of ECS and ECFS elements. Each finger needs to be equipped with one or more of these elements to maximize the level of stiffness/force feedback that is "felt" by the operator as (s)he applies activation pressure. The ECS elements are responsible for mirroring the level of mechanical resistance to the applied forces by the remote or virtual robots at specific points. The ECS element consists of a piston that is designed to move inside a sealed cylinder filled with ERF. The element stiffness is modified electrically by controlling the flow of the ERF through slots on the side of or embedded in the piston. The rate of flow is thereafter controlled electrically by electrodes facing the flowing ERF.

To control the "stiffness" of the ECS, a voltage is applied between electrodes that face the slots, and the ability of the liquid to flow is thereby affected. Thus, the slots serve as a liquid valve since the increased viscosity decreases the flow rate of the ERF and varies the stiffness that is felt. To increase the stiffness bandwidth, ranging from free flow to maximum viscosity, multiple slots are made along the piston surface. To wire such a piston to a power source, the piston and its shaft are made hollow and electric wires are connected to electrode plates mounted on either side of the slots. The inside surface of the ECS cylinder surrounding the piston is made of a metallic surface and serves as the ground and opposite polarity. A sleeve covers the piston shaft to protect it from dust, jamming or obstruction. When a voltage is applied, potential is developed through the ERF and its viscosity is altered. As a result of the increase in the ERF viscosity, the flow is slowed significantly thereby increasing resistance to external axial forces.

To produce a complete emulation of a mechanical "tele-feeling" system, the ECFS actuator is used in order to simulate remote reaction forces. This active actuator can mirror the forces at the virtual/remote site by pulling the finger or other limbs backward as dictated by the virtual reality or experienced by a remote robot. This actuator operates as an inchworm motor having active and passive elements (i.e., a braking mechanism and an expander, respectively, wherein at least one brake locks the motor position onto a shaft and the expander advances or stretches the motor forward). While the motor is stretched forward, a second brake clamps down on the shaft while the first brake is released. The process is repeated as necessary so that the actuator inches forward or backward, similar to an inchworm in nature.

Using the controllability of the resistive aspect of the ERF, a brake can be formed to support the proposed inchworm. The actuator includes of two pistons (brake element) and two electromagnetic cylinders (pusher element). Each electromagnetic cylinder further includes a coil and a ferromagnetic core integrated inside the piston. Similar to ECS, each piston has several small slots with a fixed electrode plate. When an electric field is induced between the piston anode and cylinder cathode, the viscosity of the ERF increases and the flow rate of the fluid through a piston slot decreases, thereby securing the piston to a cylinder wall therearound. When current impulse is passed through the winding, an electromagnetic field is induced and, depending on the current direction, the cylinder will either move forward or backward.

Once the key elements of MEMICA are provided, a haptic exoskeleton is developed integrating the elements at various joints. Parallel to the development of the haptic gloves, a virtual surgical emulation system is constructed using a combination of a stereo-visual display and a robot end-effector device (i.e., Phantom™) where a semi-transparent mirror creates an interface co-locating graphics and haptic interfaces. This display system offers an intuitive manipulation and interaction with the virtual environment where the user can see and feel the object in the same place.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic of a force-feedback telepresence system of the prior art wherein human operator experiences forces felt at a remote site on a haptic interface glove having force and stiffness elements integrated therewith.

Figure 2 shows an electrorheological fluid at reference and activated states

Figures 3, 3 A and 3B show a maneuverable Robonaut that performs a variety of tasks at remote sites.

Figure 4 shows a schematic of an electrically controlled stiffness element and a piston associated therewith.

Figures 5 and 6 show schematics of an electrically controlled force and stiffness actuator implemented in the present invention. Figure 7 shows a schematic sequence diagram of the operation of the electrically controlled force and stiffness actuator of Figures 5 and 6.

Figure 8 shows a schematic of the placement of the electrically controlled stiffness elements and of electrically controlled force and stiffness actuators of Figures 4, 5, 6 and 7 on an in-palm configuration of a haptic interface glove.

Figure 9 shows a side view and a rear view of a finger phalange having an electrically controlled force and stiffness actuator mounted thereon in an exoskeleton configuration.

Figure 10 shows a plurality of exoskeleton embodiments wherein a finger phalange has an electrically controlled stiffness element or an electrically controlled force and stiffness actuator mounted thereon.

Figure 11 shows two views of an exoskeleton haptic glove having a plurality of electrically controlled force and stiffness actuators and electrically controlled stiffness elements mounted thereon.

Figure 12 shows a perspective view of an illustrative integration of the present invention MEMICA System with a Reachln™ display and two Phantom™ manipulators.

Figure 13 shows a schematic of a virtual reality training tasks such as virtual surgery using the present invention MEMICA System.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a haptic interface system that consists of a pair of gloves, a headpiece or any other anthropomorphic garment that is equipped with a series of electrically controlled stiffness (ECS) elements and electrically controlled force and stiffness (ECFS) actuators. Each articulating member is equipped with one or more ECS elements and/or ECFS actuators so as to maximize the level of stiffness/force feedback that is "felt" by the operator as (s)he applies activation pressure. The ECS elements and/or ECFS actuators mirror the level of mechanical resistance to the applied forces by the remote or virtual robots at specific points. The element stiffness and/or resistance force is modified electrically by controlling the flow of an electrorheological fluid (ERF) through slots on the side of or embedded in one or two pistons. The ECS element consists of a piston that is designed to move inside a sealed cylinder filled with ERF. The rate of flow is controlled electrically by electrodes facing the flowing ERF while inside the slot. The ECFS actuator includes two pistons moving on a sealed cylinder filled with ERF fluid as in the ECS elements. The two pistons are also equipped with electromagnetic elements that can apply the required forces to actively move the pistons in the ERF fluid. Forces applied at a robot end-effector due to a compliant or rigid environment are reflected to the remote human operator using such ERF- based haptic interfaces.

The present invention can now be described with reference to the figures, in which like elements are identically numbered.

Electrically Controlled Stiffness Elements

Referring to Figure 4, the stiffness that a human operator feels will be controlled electrically via an ECS element 1, thereby affecting the flow rate of an ERF 10 through a piston 12 having a length L, an inner radius r, and an outer radius r₀. Piston 12 moves inside a sealed chamber 14 which itself is filled with ERF 10, wherein the flow rate is electrically controlled inside a piston channel (not shown) facing the flowing ERF. Two alternative piston designs may be considered for the "stiffness" control: (a) a piston having side slots so that a voltage can be applied between electrodes that are facing the slots, thereby affecting the ability of the liquid to flow; and (b) a hollow piston that includes screen electrodes placed on each of a top section and a bottom section thereof wherein slot size and electrode spacing provides design flexibility. The slots serve as liquid-valves: increasing the viscosity of the flowing ERF decreases the flow rate, thus varying the resistance that is felt by the operator that is pushing the piston. Although chamber 14 and piston 12 are shown as generally cylindrical members, it is understood that any geometric configuration may be implemented that is conducive to achieving the advantages of the present invention. Multiple slots 18 are provided along outer surface 20 of piston 12 so as to increase the stiffness/resistance bandwidth in a broad range, from free flow to maximum viscosity. Piston

12 and an associated shaft 22 are desirably hollow to accommodate wiring of piston 12 to a power source (not shown). Electric wires are connected to electrode plates (not shown) mounted on either side of slots 18.

A sleeve may be provided that covers piston shaft 22 to protect the shaft from dust, jamming or similar obstruction. In addition, a compliant bottom 28 may also be provided that compensates for any imbalance in volume above and below piston 12 caused by shaft 22. Bottom 28 is desirably fabricated from a resilient element, such as a rubber pad or a spring- loaded piston.

In the case of using slots 18, an inside surface 14a of ECS cylinder 14 surrounding piston 12 is desirably fabricated from a metallic material that serves as the ground and opposite polarity. When a voltage is applied, a potential will be developed through ERF 10 that flows through the channel, thereby altering the fluid's viscosity. Consequently, the rate of flow retards significantly so as to increase the ERF's resistance to external axial forces.

Electrically Controlled Force and Stiffness (ECFS) Actuator

Complete emulation of a mechanical "tele-feeling" system may be effected by implementation of actuators (in addition to the ECS elements) that provide feedback of remote reaction forces. Such a force feedback mechanism needs to provide both active and resistive actuation. The active actuator can mirror the forces at the virtual/remote site by pushing the finger or other limbs backward as dictated by the virtual reality or experienced by a remote robot.

Referring now to Figures 5 and 6, an ECFS actuator 31 is shown. Actuator 31 operates as an inchworm motor that includes at least two pistons 33 and 35 in coaxial alignment relative to each other and a shaft 22'. Pistons 33 and 35 constitute a brake element. Actuator 31 further includes at least a pair of electromagnetic cylinders 37 that constitutes a pusher element. Each of pistons 33 and 35 has several small channels defined therein and an electrode plate fixed thereto. When an electric field is induced between a piston anode 43 and a cylinder cathode 45, the viscosity of ERF 10 increases and the flow rate of the fluid though the piston channel decreases, thereby securing pistons 33 and 35 to cylinder wall 47.

Each electromagnetic cylinder 37 includes a winding 37a integrated therewith such that when current impulse is passed through each winding, an electromagnetic field is induced. Depending on the current direction, each cylinder 37 will either move forward or backward. This actuation principle is shown as a set of sequence diagrams in Figure 7. In operation, piston 33 is fixed relative to a housing wall 47 by activating electrode 43. Triggering electromagnetic cylinder 37 then moves second piston 35 forward. ERF 10 that is positioned between pistons 33 and 35 is then displaced backward through a channel 48. A horizontal channel (not shown) may be added at an exterior surface of housing wall 47 to increase the flow rate of the fluid. Piston 35 is thereafter activated and fixed to housing wall 47 while piston 33 is disconnected therefrom. The current in winding 37a is then reversed, reversing the polarization of respective cylinder 37 and pushing piston 33 forward relative to piston 35.

During each cycle, pistons 33 and 35 can move forward or backward with very small displacement (<1.5mm). The duration of each cycle can be close to a millisecond, corresponding to the response time of ERF 10. The ECFS actuator can then reach a speed higher than 15-cm/s with a piston displacement equal to 0.5-mm at 3-ms cycle duration. Electromagnetic cylinders 37 are adapted to perform the same force as the resistive force of the piston inside ERF 10 (i.e., about 15N).

In order to evaluate ECFS actuator 31, an electronic controller (not shown) is designed and fabricated to operate synchronously. The input to the controller is the desired force to be produced by each ECFS actuator 31. An electronic board will have several functions including, but not limited to, high voltage generator, current generation and load cell amplification. A pulse with modulation amplification having a frequency of about 200 khz is used to drive the current in windings 37a in order to reduce heating. A miniature load cell with a strain gage may be mounted on cylinder wall 47. The virtual desired force will be compared to the measured force of the load cell. The force error will be processed by a linear state-space-controller where the gains will be selected using optimal and/or robust control design criteria. Adaptive controllers will be considered to assure good performance of the controller for large virtual force changes or unknown environment.

MEMICA Breadboard Haptic Glove

Once the key elements of MEMICA are developed, a haptic exoskeleton may be constructed so as to integrate the ECS elements and ECFS actuators at various joints. Figure 8 depicts an illustrative example, wherein a MEMICA-glove 50 is derived that requires a series of ECS elements 1 and ECFS actuators 31 placed in an in-palm configuration. ECS elements 1 and/or ECFS actuators 31 are responsible for mirroring the level of mechanical resistance to the applied forces at specific virtual joints/points that is being mirrored. Each finger 52, therefore, needs to be equipped with one or more of elements 1 and 31 to maximize the level of compliance/force feedback that is "felt" by the operator as the activation pressure is applied. The ECS elements 1 and/or ECFS actuators 31 can be placed inside the palm as shown in Figure 8 or in an exoskeleton configuration (as further shown in Figures 9, 10 and 11 and described hereinbelow). In such configurations, the natural motion of the hand will be unrestricted, enabling application of an independent force (uncoupled) on each phalange so as to maximize the level of stiffness/force feedback that is "felt" by the operator.

Referring further to Figure 9, glove 50 accommodates a large number of hand sizes and geometries via mounting of ECFS actuator 31 or ECS elements 1 on an adjustable ring 54. Ring 54 is desirably fabricated from a pair of flexible strips 54a removably attached to one another with one or more securement elements 56 made from a closure material such as Velcro or the like. Once elements 56 are secured, strips 54a form a very rigid ring. The rigid ring will be able to support large forces without being distorted and without risk of pain or stagnation of blood in the presence of such large forces.

During this phase, different mounting mechanisms may be implemented, some of which are schematically illustrated in Figure 10. An arched actuator 60 as depicted in drawing (a) of Figure 10 presents an ergonomic solution that has better fitting with finger motion and geometry and, unlike a pneumatic cylinder, is feasible to fabricate. Since the ERF viscosity is higher than that for air, there is no need for tight tolerance for the ECFS piston and its corresponding cylinder. A second embodiment shown in drawing (b) of Figure 10 uses a curved sliding rail 62, which is also suitable for finger motion. A third embodiment as shown in drawing (c) uses an adjustable tendon 64 connected directly to actuator 31, wherein tendon length is adjustable to the user phalange length. Different human factor tests can be performed when evaluating the operation of one finger mechanism so as to evaluate the comfort, the adaptability and the resistance feeling with different users. It is also possible to evaluate the accuracy of the applied force/resistance.

Once the appropriate exoskeleton mechanism is chosen, a complete haptic glove 50' is achieved as is more fully illustrated in Figure 11. Glove 50' includes 16 actuators: 3 actuators for the thumb (2 for the flexion motion and 1 for the abduction/adduction motion); 4 actuators for the index finger (3 for the flexion motion and 1 for the abduction/adduction motion) and 3 actuators for the remaining fingers (flexion only). For precision grasping with the thumb and the index finger, where abduction/adduction motion is involved, actuators that would resist this motion can be further integrated.

To accurately measure the position and movement of the fingers, an angular or linear sensor 70 is integrated on each ECFS actuator 31 of MEMICA gloves 50 and 50'. Hall Effect Transducers are preferable due to their accuracy, compact size and zero friction, however, any such sensor that is conducive to the operation of the present invention may be utilized. A kinematics model and a calibration process assists MEMICA glove 50 and 50' to accurately match different users' hands, allowing the haptic glove to produce a more stable force feedback on each finger joint when collision with virtual object is detected. MEMICA Virtual Training / Simulation System

Figure 12 shows an integrated MEMICA training/simulation system wherein a pair of MEMICA gloves 50 is integrated with an interactive computer modeling system 73 (such as a Reachln™ display, a trademark of Reachln Technologies of Stockholm) and two force feedback six-degree-of-freedom manipulators 75 (such as those provided by a PHANTOM™ device, a trademark of SensAble Technologies, Inc. of Woburn, Massachusetts). At least one MEMICA glove 50 is affixed to an end-effector (not shown) defined at an extremity of each manipulator 75, shown herein as a robotic arm. Manipulator 75 is a force feedback robot manipulator that provides accurate measurement of the position and orientation of glove 50. Manipulator 75 also applies grounding forces and hand posture to glove 50, thereby providing corresponding grasping and manipulation forces to a human operator. A desirable advantage of such a dual force-feedback system (i.e., the combination of an arm and a hand- master) is the high haptic bandwidth of both glove 50 and manipulator 75. The bandwidth of this system desirably exceeds 320 Hz, which is a level where the human finger cannot discriminate between two consecutive force input signals. This system will therefore provide multi-degree of freedom force/moment feeling in many different points of the hand and with enhanced accuracy and intuition.

Referring now to Figure 13, an example of using our integrated MEMICA haptic system in a medical training task is shown. A medical doctor can grasp and manipulate a virtual catheter using MEMICA glove 50. Taking advantage of the empty hand with MEMICA glove 50, a real catheter can be grasped at the same time with the virtual catheter. This allows perfect calibration of the position and the force measured by glove 50 and thus calculated in the virtual environment during the manipulation. The second stage of the integration will entail combining the visual (virtual) fluoroscopic feedback of the catheter advancing through the model with the motion of the MEMICA gloves. This will allow the human operator to interact and evaluate the accuracy of the tactile feedback compared to the visual feedback. After the system is demonstrated to operate at the level needed to perform an endovascular procedure, a stent or endoluminal graft can be deployed within the virtual model.

The novel MEMICA haptic interface system of the present invention uses electrorheological fluid (ERF) based elements and actuators that allow reproduction of the tactile interaction of human-controlled manipulators in a remote or virtual environment. With this technology, the user will be able to feel a force and stiffness on each joint via devices that can accurately mirror actual reaction compliance and forces with very high bandwidth. The use of electrorheological fluids enables development of many useful devices that support the need for a haptic interface in such areas as automation, robotics, medicine, games, sport and the like. Beneficiaries of the present invention further include patients requiring mobile assistance who can don the present invention as an exoskeleton that complements residual anthropomorphic movement. The present invention also benefits soldiers in the field who can deploy detonation devices or serve reconnaissance missions using haptic interface mechanisms. Astronauts and other participants in space exploration can further benefit from the present invention to establish the "virtual presence" of space explorers via robotic devices such as Robonaut. Improved medical and technical training for intricate procedures, such as minimally invasive virtual or remote surgical procedures for both terrestrial and planetary applications at various gravity levels and climatic extremes, are also achieved. As an education tool employing virtual reality, this MEMICA system supports changing training paradigms, such as the trend in medical schools towards replacing cadaver specimens with computerized models of human anatomy. As a result of the ERF properties and the small size of the actuators, these devices can be made more compact while delivering larger forces and compliance.

Various changes to the foregoing described and shown methods and corresponding structures would now be evident to those skilled in the art. The matter set forth in the foregoing description and accompanying drawings is therefore offered by way of illustration only and not as a limitation. Accordingly, the particularly disclosed scope of the invention is set forth in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A haptic interface mechanism that enables a human operator to accurately feel stiffness and forces at a remote or virtual site, comprising:

at least one electrorheological fluid-based component coupled with an articulating member wherein forces on said member are transmitted to said operator via a change in a viscosity of said fluid in proportion to a force to be transmitted.

2. The haptic interface mechanism of claim 1 wherein said component includes at least one electrically controlled stiffness element

3. The haptic interface mechanism of claim 2 wherein said element includes a piston having a longitudinal axis therethrough, said piston reciprocatingly housed within a sealed member having a smooth interior surface that defines a piston channel therethrough in which said fluid is contained.

4. The haptic interface mechanism of claim 3 wherein said interior surface is fabricated from a conductive material

5. The haptic interface mechanism of claim 3 wherein said piston includes at least one longitudinal slot defined on an exterior surface of said piston substantially parallel to said longitudinal axis to increase said viscosity and consequently decrease a flow rate of said fluid.

6. The haptic interface mechanism of claim 5 wherein said piston includes an elongate shaft depending longitudinally therefrom in coaxial relation to said longitudinal axis.

7. The haptic interface mechanism of claim 6 further including a sleeve that covers said shaft so as to protect said shaft from obstruction.

8. The haptic interface mechanism of claim 6 further including a compliant bottom fabricated from a resilient element to compensate for imbalance in volume above and below said piston induced by said shaft.

9. The haptic interface mechanism of claim 5 further including at least one electrode mounted on either side of said slot wherein said electrode is electrically coupled to at least one electric wire.

10. The haptic interface mechanism of claim 5 further including at least one screen electrode placed on each of a top section and a bottom section of said piston.

11. The haptic interface mechanism of claim 1 wherein said component includes at least one electrically controlled force and stiffness actuator.

12. The haptic interface mechanism of claim 11 wherein said actuator includes at least one braking mechanism and at least one pusher mechanism.

13. The haptic interface mechanism of claim 12 wherein said braking mechanism includes at least two pistons in reciprocating alignment within an enclosed member having a smooth interior surface that defines a piston channel therethrough in which said fluid is contained.

14. The haptic interface mechanism of claim 13 wherein each said piston has several channels defined therein through which said fluid flows.

15. The haptic interface mechanism of claim 14 further including at least one electrode affixed to each said piston.

16. The haptic interface mechanism of claim 15 wherein said enclosed member has a cylinder cathode integral therewith.

17. The haptic interface mechanism of claim 12 wherein said pusher mechanism includes at least a pair of electromagnetic cylinders.

18. The haptic interface mechanism of claim 17 wherein each said electromagnetic cylinder includes a winding integrated therewith to induce an electromagnetic field when current impulse is passed therethrough.

19. The haptic interface mechanism of claim 1 further including an electronic controller electrically coupled thereto wherein said forces to be transmitted to said component are input to said controller.

20. The haptic interface mechanism of claim 1 wherein said mechanism includes an anthropomoφhic garment having a plurality of said components integrated therewith.

21. The haptic interface mechanism of claim 20 wherein said garment includes an exoskeleton includes having a plurality of said components mounted thereon.

22. The haptic interface mechanism of claim 21 wherein each said component includes a sensor in mechanical and electrical communication therewith.

23. The haptic interface mechanism of claim 22 wherein said sensor is a Hall Effect transducer.

24. The haptic interface mechanism of claim 20 wherein at least one said garment is integrated with an interactive computer modeling system.

25. The haptic interface mechanism of claim 24 wherein said garment and said interactive computer modeling system are further integrated with at least one force feedback multiple degree-of-freedom manipulator.

26. The haptic interface mechanism of claim 25 wherein said garment is affixed to an end-effector defined at an extremity of a robotic arm.

27. A remote mechanical mirroring system using controlled stiffness and actuators, comprising:

at least one haptic interface mechanism that enables a human operator to accurately feel stiffness and forces at a remote or virtual site, said mechanism comprising:

at least one electrorheological fluid-based component coupled with an articulating member wherein forces on said member are transmitted to said operator via a change in a viscosity of said fluid in proportion to a force to be transmitted;

wherein said at least one said haptic interface is affixed to an end-effector defined at an extremity of a robotic arm and integrated with an interactive computer modeling system and further integrated with at least one force feedback multiple degree-of-freedom manipulator.

28. The system of claim 27 wherein said component includes at least one electrically controlled stiffness element

29. The system of claim 28 wherein said element includes a piston having a longitudinal axis therethrough, said piston reciprocatingly housed within a sealed member having a smooth interior surface that defines a piston channel therethrough in which said fluid is contained.

30. The system of claim 29 wherein said interior surface is fabricated from a conductive material

31. The system of claim 29 wherein said piston includes at least one longitudinal slot defined on an exterior surface of said piston substantially parallel to said longitudinal axis to increase said viscosity and consequently decrease a flow rate of said fluid.

32. The system of claim 31 wherein said piston includes an elongate shaft depending longitudinally therefrom in coaxial relation to said longitudinal axis.

33. The system of claim 32 further including a sleeve that covers said shaft so as to protect said shaft from obstruction.

34. The system of claim 32 further including a compliant bottom fabricated from a resilient element to compensate for an imbalance in volume above and below said piston induced by said shaft.

35. The system of claim 31 further including at least one electrode mounted on either side of said slot wherein said electrode is electrically coupled to at least one electric wire.

36. The system of claim 31 further including at least one screen electrode placed on each of a top section and a bottom section of said piston.

37. The system of claim 27 wherein said component includes at least one electrically controlled force and stiffness actuator.

38. The system of claim 37 wherein said actuator includes at least one braking mechanism and at least one pusher mechanism.

39. The system of claim 38 wherein said braking mechanism includes at least two pistons in reciprocating alignment within a housing member having a smooth interior surface that defines a piston channel therethrough in which said fluid is contained.

40. The system of claim 39 wherein each said piston has several channels defined therein through which said fluid flows.

41. The system of claim 40 further including at least one electrode affixed to each said piston.

42. The system of claim 41 wherein said cylindrical member has a cylinder cathode integral therewith.

43. The system of claim 38 wherein said pusher mechanism includes at least a pair of electromagnetic cylinders.

44. The system of claim 43 wherein each said electromagnetic cylinder includes a winding integrated therewith to induce an electromagnetic field when current impulse is passed therethrough.

45. The system of claim 27 further including an electronic controller electrically coupled thereto wherein said forces to be transmitted to said component are input to said controller.

46. The system of claim 27 wherein said mechanism includes an anthropomoφhic garment having a plurality of said components integrated therewith.

47. The system of claim 46 wherein said garment includes an exoskeleton includes having a plurality of said components mounted thereon.

48. The system of claim 47 wherein each said component includes a sensor in mechanical and electrical communication therewith.

49. The system of claim 48 wherein said sensor is a Hall Effect transducer.

50. The system of claim 27 further including at least one virtual medical device to allow a human operator to interact and evaluate accuracy of tactile feedback compared to corresponding visual feedback.