Daniel A. Bennett

A Multigrasp Hand Prosthesis for Providing Precision and Conformal Grasps

This paper presents the design of an anthropomorphic prosthetic hand that incorporates four motor units in a unique configuration to explicitly provide both precision and conformal grasp capability. The paper describes the design of the hand prosthesis, and additionally describes the design of an embedded control system located in the palm of the hand that enables self-contained control of hand movement. Following the design description, the paper provides experimental characterizations of hand performance, including digit force capability, bandwidth of digit movement, physical properties such as size and mass, and electrical power measurements during activities of daily living.

Preliminary functional assessment of a multigrasp myoelectric prosthesis

The authors have previously described a multigrasp hand prosthesis prototype, and a two-site surface EMG based multigrasp control interface for its control. In this paper, the authors present a preliminary assessment of the efficacy of the prosthesis and multigrasp controller in performing tasks requiring interaction and manipulation. The authors use as a performance measure the Southampton Hand Assessment Procedure (SHAP), which entails manipulation of various objects designed to emulate activities of daily living, and provides a set of scores that indicate level of functionality in various types of hand function. In this preliminary assessment, a single non-amputee subject performed the SHAP while wearing the multigrasp prosthesis via an able-bodied adaptor. The results from this testing are presented, and compared to recently published SHAP results obtained with commercially available single-grasp and multigrasp prosthetic hands.

Design of a hand prosthesis with precision and conformal grasp capability

This paper presents the design of an anthropomorphic prosthetic hand that provides both precision and conformal grasp capability. Specifically, the design of the hand dedicates three actuators in a direct-drive manner to achieving precision grasp capability. The design additionally dedicates one actuator and six degrees of freedom, in addition to a compliant coupling, to providing a conformal grasping capability to the amputee. The design of the hand is described in this paper, and the various degrees of actuation are characterized with respect to grasp forces and finger speeds.

Design of a Myoelectric Transhumeral Prosthesis

This paper describes a transhumeral prosthesis prototype intended for the purpose of experimentally investigating design features and control strategies for the control of transhumeral prostheses. This paper specifically focuses on the design and performance characterization of a powered wrist rotator and powered elbow joint, in addition to the embedded system that controls them. In addition to outlining design objectives associated with the wrist and elbow joints, this paper describes the design of both joints, and the embedded system that provides control of them and the arm system. Experimental data are presented that characterizes the performance characteristics of both joints, including data associated with electrical power consumption and audible noise. The arm prosthesis described here is intended to be used with a multigrasp hand prosthesis, previously published by the authors.

Design and characterization of a powered elbow prosthesis

This paper describes the design of a powered elbow prosthesis, which incorporates a belt and cable drive transmission with a brushless DC motor to achieve an output torque of approximately 18.4 Nm, a backdrive torque of 1.5 Nm, and a speed of up to 360 deg/s while remaining within the anthropomorphic envelope with regard to mass and size. The measured torque and speed of the prosthesis is commensurate with nominal capability of the natural limb (for purposes of performing activities of daily living).

Functional assessment of the Vanderbilt Multigrasp myoelectric hand: a continuing case study.

This paper presents a case study involving the functional assessment of the Vanderbilt Multigrasp (VMG) hand prosthesis on a single transradial amputee subject. In particular, a transradial amputee subject performed the Southampton Hand Assessment Procedure (SHAP) using the hand prosthesis and multigrasp myoelectric controller in a series of experimental sessions occurring over a multi-week time span. The subjects index of function (IoF) improved with each session, although essentially plateaued after the fourth session, resulting in a IoF score of 87, which compares favorably to SHAP scores published in previous studies.

Functional assessment of a Multigrasp Myoelectric prosthesis: An amputee case study

This work presents a functional assessment of the Vanderbilt Multigrasp Hand prosthesis and Multigrasp Myoelectric Control method which the authors have previously described. In the study, a transradial amputee utilized the prosthetic system to perform the Southampton Hand Assessment Procedure (SHAP), which involves manipulation tasks designed to simulate the activities of daily living. The results of the study indicate 81% restoration of typical hand function and compare favorably to recently published SHAP results for commercially available single-grasp and multigrasp prosthetic hands. A video of the assessment is included as supplementary material.

IMU-Based Wrist Rotation Control of a Transradial Myoelectric Prosthesis

This paper describes a control method intended to facilitate improved control of a myoelectric prosthesis containing a wrist rotator. Rather than exclusively utilizing electromyogram (EMG) for the control of all myoelectric components (e.g., a hand and a wrist), the proposed controller utilizes inertial measurement (from six-axis inertial measurement unit (IMU)) to sense upper arm abduction/adduction, and uses this input to command a wrist rotation velocity. As such, the controller essentially substitutes shoulder abduction/adduction in place of agonist/antagonist EMG to control wrist angular velocity, which preserves EMG for control of the hand (or other arm components). As a preliminary assessment of efficacy, the control method was implemented on a transradial prosthesis prototype with a powered wrist rotator and hand, and experimentally assessed on five able-bodied subjects who wore the prototype using an able-bodied adaptor and one transradial amputee subject while performing assessments representative of activities of daily living. The assessments compared the (timed) performance of the combined EMG/ IMU-based control method with a (conventional) sequential EMG control approach. Results of the assessment indicate that the able-bodied subjects were able to perform the tasks 33% faster on average with the EMG/IMU-based method, relative to a conventional sequential EMG method. The same assessment was subsequently conducted using a single transradial amputee subject, which resulted in similar performance trends, although with a somewhat lessened effect size—specifically, the amputee subject was on average 22% faster in performing tasks with the IMU-based controller.

Efficacy of coordinating shoulder and elbow motion in a myoelectric transhumeral prosthesis in reaching tasks

This paper presents a control approach for myoelectric transhumeral prostheses that coordinates the movement of the elbow joint with the movement of the (intact) shoulder. The method combines input from a pair of surface electromyograms (EMG) inputs with information from an inertia measurement unit (IMU) to provide coordinated control of the joints, as described in the paper. In order to assess the efficacy of the control method, experiments were conducted on six healthy subjects using a virtual environment, comparing their ability to perform various pick-and-place tasks, specifically requiring that they pick a virtual ball from a given location and place it in a virtual box, which changed location randomly. The time required to complete a series of pick-and-place tasks using the coordinated control approach was compared to the time required to complete the tasks using a conventional sequential control approach. For these experiments, the average task completion time across all sessions and subjects was 12.8 s using the conventional sequential control approach, versus 8.7 s using the coordinated control approach (i.e., subjects performed the task 32% faster with the proposed approach), indicating that the proposed approach provides improved performance relative to the conventional approach.