Hybrid Control of the Berkeley Lower Extremity Exoskeleton (BLEEX)

Abstract

The first functional load-carrying and energetically autonomous exoskeleton 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 BLEEX sensitivity amplification controller, based on positive feedback, was designed to increase the closed loop system sensitivity to its wearer’s forces and torques without any direct measurement from the wearer. The controller was successful at allowing natural and unobstructed load support for the pilot. This article presents an improved control scheme we call “mixed” 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 torso and backpack) and the sensitivity amplification controller is used for the swing leg. The controller is also designed to smoothly transitions between these two schemes as the pilot walks. With mixed 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.

Perceiving and predicting the intended motion with human-machine interaction force for walking assistive exoskeleton robot

“…The assistance coefficient =0. 8 A , this means exoskeleton can save 20% energy for the human, and user only need to provide 80% of the original muscle torque. Use (8), (9) and (10) 3) The result analysis of simulation: The tracking performance is shown in Fig.…”

“…The scale of support period is larger than swing period, which accounts for about 60% of the entire cycle, while swing period is 40%. During the support period, On the one hand, the stance leg should have characteristics of load-bearing, not only does it has to overcome its own gravity, but also supports the entire torso and payload [8]. On the other hand, the stance leg goes through a relatively small range of motion.…”

A human motion prediction algorithm for Non-binding Lower Extremity Exoskeleton

“…In 2004, a team from University of California Berkeley unveiled their exoskeleton "BLEEX". Driven by hydraulic actuators, the BLEEX has 15 DOFs in total [3][4]. HAL was first announced in 1999 by University of Tsukuba.…”

“…The human motion prediction problem has to be settled urgently in the NBLEX system where the pilot and the exoskeleton are apart. BLEEX uses the sensitivity amplification control to detect human motion [4], HAL gets the commands from the EMG signals [5]. In the power assisting suit for assisting nurse labor developed by Keijiro [9], a muscle hardness sensor is created to predict human motion.…”

Power Assist Control Based on Human Motion Estimation Using Motion Sensors for Powered Exoskeleton without Binding Legs

“…Another approach is based on a force sensor/switch. Berkeley Lower Extremity Exoskeleton (BLEEX) [18][19][20][21] uses pressure sensors that measure the force between the shoe of the powered exoskeleton and the foot of the wearer to control the exoskeleton according to the configuration of the foot relative to the ground. Sano et al [22,23] also proposed using force sensors attached to the bottom of the wearer's feet to detect the pressure between the shoes of the exoskeleton and the ground.…”