Experimental validation of imposed safety regions for neural controlled human patient self-feeding using the modular prosthetic limb

This paper presents the experimental validation of software-based safety features implemented during the control of a prosthetic limb in self-feeding tasks with a human patient. To ensure safe operation during patient controlled movements of the limb, velocity-based virtual fixtures are constructed with respect to the patient's location and orientation relative to the limb. These imposed virtual fixtures or safety zones modulate the allowable movement direction and speed of the limb to ensure patient safety during commanded limb trajectories directed toward the patient's body or environmental obstacles. In this implementation, the Modular Prosthetic Limb (MPL) will be controlled by a quadriplegic patient using implanted intracortical electrodes. These virtual fixtures leverage existing sensors internal to the MPL and operate in conjunction with the existing limb control. Validation of the virtual fixtures was conducted by executing a recorded set of limb control inputs while collecting both direct feedback from the limb sensors and ground truth measurements of the limb configuration using a Vicon tracking system. Analysis of the collected data indicates that the system performed within the limitations prescribed by the imposed virtual fixtures. This successful implementation and validation enabled the approved clinical use of the MPL system for a neural controlled self-feeding task.