Hybrid Control of the Berkeley Lower Extremity Exoskeleton (BLEEX)

Abstract

The Berkeley Lower Extremity Exoskeleton is the first functional energetically autonomous load carrying human exoskeleton and was demonstrated at U.C. Berkeley, walking at the average speed of 0.9 m/s (2 mph) while carrying a 34 kg (75 lb) payload. The original published controller, called the BLEEX Sensitivity Amplification Controller, was based on positive feedback and was designed to increase the closed loop system sensitivity to its wearer's forces and torques without any direct measurement from the wearer. This controller was successful at allowing natural and unobstructed load support for the pilot. This article presents an improved control scheme we call "hybrid" BLEEX control that adds robustness to changing BLEEX backpack payload. The walking gait cycle is divided into stance control and swing control phases. Position control is used for the BLEEX stance leg (including the torso and backpack) and a sensitivity amplification controller is used for the swing leg. The controller is also designed to smoothly transition between these two schemes as the pilot walks. With hybrid control, the controller does not require a good model of the BLEEX torso and payload, which is difficult to obtain and subject to change as payload is added and removed. As a tradeoff, the position control used in this method requires the human to wear seven inclinometers to measure human limb and torso angles. These additional sensors require careful design to securely fasten them to the human and increase the time to don and doff BLEEX.

Modelling and simulation of a system for verticalization and aiding the motion of individuals suffering from paresis of the lower limbs

“…the rigidity of the applied coupling, spatial configuration of the couplings, mass of the device or the user's height on the resultant angular errors. In the literature related to designing exoskeletons one may find reports on studies illustrating the differences between angular movements of the joints and the articulations [18], yet they cannot be compared with the obtained results because of the accepted way of controlling the BLEEX robot, so-called master-slave control, where a very significant matter is the value of the delay of the robot motion (slave) with respect to the motion of a body part (master).…”

Lower-Limb Wearable Exoskeleton

“…Kazerooni et. al., proposed the application of proportional control of position for the Bleex system, a powered lower extremity exoskeleton for human strength augmentation during locomotion (Kazerooni et. al., 2003).…”

Current Work in the Human-Machine Interface for Ergonomic Intervention with Exoskeletons

“…A man-amplifier was a "powered suit of armor" which could augment a soldier's lifting and carrying capabilities (Kazerooni, Steger, & Huang, 2006).…”