Showing papers by "Michael A. Peshkin published in 2005"

KineAssist: a robotic overground gait and balance training device

Abstract: The KineAssist is a robotic device for gait and balance training. A user-needs analysis led us to focus on increasing the level of challenge to a patient's ability to maintain balance during gait training, and also on maintaining direct involvement of a physical therapist (rather than attempting robotic replacement.) The KineAssist provides partial body weight support and postural torques on the torso; allows many axes of motion of the trunk as well as of the pelvis; leaves the patient's legs accessible to a physical therapist during walking; servo-follows a patient's walking motions overground in forward, rotation, and sidestepping directions; and catches a patient who begins to fall. Design and development of the KineAssist proceeded more rapidly in the context of a small company than would have been possible in most research contexts. A prototype KineAssist has been constructed, and has received FDA approval and IRB clearance for initial human studies. We describe the KineAssist's motivation, design, and use.

Increasing the impedance range of a haptic display by adding electrical damping

Abstract: This work examines electrical damping as a means for improving haptic display performance. Specifically, electrical damping, like its mechanical counterpart, can significantly reduce the occurrences of limit cycle oscillations at high impedance boundaries in virtual environments. Furthermore, electrical damping has a number of advantages including its simplicity of design and the ease at which it can be made frequency dependent so that it does not adversely affect a device's low impedance range. This work examines the theoretical behavior and practical application of frequency dependent electrical damping as it applies to haptic displays. Data is presented illustrating a significant increase in the range of virtual wall behaviors that a one degree-of-freedom device is capable of displaying when electrical damping is added.

MARIONET: An exotendon-driven rotary series elastic actuator for exerting joint torque

Abstract: A cable-driven, rotary series elastic actuator named MARIONET (moment arm adjustment for remote induction of net effective torque) is introduced as a novel means to deliver torque to a joint. Its advantages include remote actuation, independent control of compliance and equilibrium, and in future versions, the ability to span multiple joints. This cable-driven, compliant mechanism should prove very useful in a variety of human-robot interactions. Here we present a single joint device evaluated in terms of its position and torque step responses, its ability to follow a minimum jerk trajectory, and its ability to create torque fields. Results show that this device behaves as planned with several important limitations. We conclude with potential applications of this type of mechanism.

Multifunctional Whisker Arrays for Distance Detection, Terrain Mapping, and Object Feature Extraction

Abstract: Several species of animals use whiskers to accurately navigate and explore objects in the absence of vision. We have developed inexpensive arrays of artificial whiskers based on strain-gage and Flex Sensor technologies that can be used either in passive (“dragging”) mode, or in active (“whisking”) mode. In the present work we explore the range of functions that whisker arrays can serve on a rover. We demonstrate that when mounted on a rover, whisker arrays can (1) Detect obstacles and determine obstacle distance (2) Map terrain features (3) Determine ground and surface texture (4) Provide an estimate of rover speed (5) Identify “slip” of the rover wheels, and (6) Perform 3-dimensional extraction of object shape. We discuss the potential use of whisker arrays on planetary rovers and as an investigative tool for exploring the encoding of sensory information in the nervous system of animals.

Walking and balance exercise device

Abstract: A pelvic support unit is coupled to a base (110), by a powered vertical force actuator mechanism. A torso support unit (600), which is affixed to the patient independently of the pelvic support unit, is connected to the base (110) by one or more powered articulations which are actuable around respective axes of motion. Sensors sense the linear and angular displacement of the pelvic support unit and the torso support unit. A control unit is coupled to these sensors and, responsive to signals from them, selectively control the displacement actuator and articulation(s). Wheel modules are independently powered to both rotate and steer, and, responsive to the control unit, are capable of rolling the exercise device in a direction of travel intended by the patient.

Kinesthetic interaction

Abstract: In physical and occupational therapy two people interact through force and motion. Other common examples of this interaction include lifting and moving a bulky object, teaching manual skills, dancing, and handing off a baton or a drinking glass. These tasks involve kinesthetic interaction, a communication channel distinct from spoken language and gestures. Understanding kinesthetic interaction should be important in designing robots to assist with physical and occupational therapy. In this paper we describe our experiments on kinesthetic interaction between two people cooperating on a 1 degree of freedom task. We characterize the interaction forces between the two people, dividing them into a productive "net force" and an orthogonal "difference force." Our results suggest three effects (1) an emergent specialization of the two participants into different roles, (2) an oscillation of forces at about 8 Hz, and (3) a steady force in opposition to one another that could be analogous to co-contraction in an individual.

Static Single-Arm Force Generation With Kinematic Constraints

Abstract: Smooth, frictionless, kinematic constraints on the motion of a grasped object reduce the motion freedoms at the hand, but add force freedoms, that is, force directions that do not affect the motion...

Human interaction with passive assistive robots

Abstract: We are studying the use of programmable constraint machines for rehabilitation and as assistive devices in materials handling. In this paper we describe initial experiments in human interaction with a two-joint passive programmable constraint device, or cobot. The user grasps the manipulandum at a handle, and the manipulandum implements a smooth, hard, low friction constraint curve. Initial experiments in reaching tasks subject to such a constraint show that subjects apply significant forces against the constraint, in a manner dependent on the movement speed and constraint shape. These forces can be broken into passive forces (due simply to the dynamics of the human arm) and forces actively generated by the muscles. Some motor adaptation is also evident.

Haptic Interaction With Constrained Dynamic Systems

Abstract: In this paper we are concerned with allowing the operator of a haptic display to interact with virtual systems having significant inertial dynamics and realistic constraints. We review the mathematical structure arising from the kinetic energy metric, required to create a virtual dynamics simulation consisting of rigid-body dynamics along with holonomic and/or nonholonomic motion constraints. We develop an admittance controller composed of feedforward and feedback terms, while preserving the integrity of the intended virtual dynamics simulation. This controller is implemented on the Cobotic Hand Controller, an admittance-type haptic display, and two examples are discussed.

Real time stiffness display interface device for perception of virtual soft object

Abstract: A novel method based on deformable length of elastic element control (DLEEC) to realize the stiffness display for perception of virtual soft object is proposed, and the stiffness display interface device has been developed and is presented. The stiffness display interface device is composed of a thin elastic beam and an actuator to adjust the length of the beam. The deformation of the beam under a force is proportional to the third power of the beam length. By controlling the beam length, the stiffness display device can reproduce the stiffness of the virtual object from very soft to hard, so that the human fingertip can feel it as if he directly touches with the virtual object by interacting with the device. A real time position control algorithm is employed to guarantee the real time stiffness display.

Design and performance of a high fidelity, low mass, linear haptic display

Abstract: We built a high fidelity, low mass, linear haptic display, with a peak force output of 8.5 Newtons, continuous force output of 1.3 Newtons, range of motion of approximately 15 millimeters, sensing resolution of 0.5 microns, and a -3 dB bandwidth of approximately 550 Hz. By having low apparent mass of approximately 5 grams, we can realistically render linear switches, which themselves have a moving mass of only a few grams. This device utilizes a low inertia rotary motor, but over only a limited range of motion, allowing it to be driven without commutation. We constructed a linear, current controlled amplifier to drive the system. Additionally, the motor windings allow us to use electrical damping to add physical damping to the system to improve its performance.

A Draw-In Sensor for Process Control and Optimization

Abstract: Sheet metal forming is one of the major processes in manufacturing and is broadly used due to its high degree of design flexibility and low cost. In the sheet metal forming process, draw-in (planar movement of a sheet periphery) frequently occurs and is one of the most dominated indicators on the success of a forming process. Currently, monitoring and controlling draw-in during each stamping operation requires either time-consuming setup or a significant die modification. Most devices have been used only in laboratory settings. Our goal is to design a draw-in sensor providing high sensitivity in monitoring; ease of setup, measurement and controlling; and eventually be implemented in industry. Our design is based on the mutual inductance principle, which we considered physical factors affecting the characteristics of the draw-in sensor. Two different configurations, single-transducer and double-transducer of our draw-in sensors have been designed and tested. The results showed good linearity, especially for the double-transducer case. The output of the draw-in sensor was affected by the type of sheet metal, dimension of the transducer, and the distance between the transducer and the testing sheet metal. It was found that the result was insensitive to the waviness of the sheet metal if sheet thickness was thin. The invention, implementation, and integration of the draw-in sensor will have an enormous impact on revolutionizing the control of stamping process, will provide solid ground for process variation and uncertainty studies, and ultimately will affect the design decision process.

High performance Cobotics

Abstract: Cobots are a class of robots that use continuously variable transmissions to develop high fidelity programmable constraint surfaces. Cobots consume very little electrical power even when providing high output forces, and their transmissions are highly efficient across a broad range of transmission ratios. Cobotic transmissions also have the ability to act either as a brake or to become entirely free. The design and performance of the cobotic hand controller, a recently developed six-degree-of-freedom haptic display, is reviewed. This device illustrates the high dynamic range and low power consumption achievable by cobots. A thorough comparison of the power efficiency of a cobotic system versus a conventional electro-mechanical system is provided.

Semi‐autonomous Telerobotic Manipulation: A Viable Approach for Space Structure Deployment and Maintenance

Abstract: Future space explorations necessitate manipulation of space structures in support of extra vehicular activities or extraterrestrial resource exploitation In these tasks robots are expected to assist or replace human crew to alleviate human risk and enhance task performance However due to the vastly unstructured and unpredictable environmental conditions, automation of robotic task is virtually impossible and thus teleoperation is expected to be employed However teleoperation is extremely slow and inefficient To improve task efficiency of teleoperation, this work introduces semi‐autonomous telerobotic operation technology Key technological innovations include implementation of reactive agent based robotic architecture and enhanced operator interface that renders virtual fixture