Motion generation through biologically-inspired torque pulses

Traditional robot controllers are not designed to produce human-like reactive motion—movements lasting tens of sample periods and requiring large accelerations. One of the major obstacles to producing reactive motions with contemporary controllers is that they rely on kinematic commands. The performance of short duration motions requiring large accelerations is dominated by the motion's dynamics; kinematic commands without an accurate dynamic model of the robot and task will lead to poor performance. Conversely, this paper presents a biologically inspired “torque command” that allows the dynamics of the motion to be communicated to the controller. The commands can be produced with only minor modifications to any existing control scheme that will not impact traditional operation. In addition, sensory input can be mapped directly to presented commands for latency sensitive tasks. The ability of the new commands to express a broad range of motions with a small number of parameters is shown experimentally. The experimental results also show that the presented torque commands can be used to learn a ball intercept task.

I. Introduction

Prosthetics controlled by the human brain are currently a reality [1], [2], but are limited to slow, controlled motions. One major reason behind this is the treatment of the user as a motion source, discarding important information about the motion's dynamics [3]. The brain is capable of low-level limb control using muscle activations, similar to robot joint torques. Allowing motions to be specified in such a format will provide the user more control over the device and a mechanism for producing reactive motions. In addition, the ability to produce biological-like reactive motion is becoming more important as robots assume a larger domestic role. If the robotic cat for monitoring the health of an elderly person in [4] could skillfully swat at a string it would be more likely to be treated as a natural part of the environment.