Hami Kazerooni

On the mechanical design of the Berkeley Lower Extremity Exoskeleton (BLEEX)

The first energetically autonomous lower extremity exoskeleton capable of carrying a payload has been demonstrated at U.C. Berkeley. This paper summarizes the mechanical design of the Berkeley Lower Extremity Exoskeleton (BLEEX). The anthropomorphically-based BLEEX has seven degrees of freedom per leg, four of which are powered by linear hydraulic actuators. The selection of the degrees of freedom and their ranges of motion are described. Additionally, the significant design aspects of the major BLEEX components are covered.

On the Biomimetic Design of the Berkeley Lower Extremity Exoskeleton (BLEEX)

Many places in the world are too rugged or enclosed for vehicles to access. Even today, material transport to such areas is limited to manual labor and beasts of burden. Modern advancements in wearable robotics may make those methods obsolete. Lower extremity exoskeletons seek to supplement the intelligence and sensory systems of a human with the significant strength and endurance of a pair of wearable robotic legs that support a payload. This paper outlines the use of Clinical Gait Analysis data as the framework for the design of such a system at UC Berkeley.

A controller design framework for telerobotic systems

A framework for designing a telerobotic system controller is presented. This controller is designed so the dynamic behaviors of the master robot and the slave robot are functions of each other. These functions, which the designer chooses based upon the application, are described, and a control architecture is proposed to achieve these functions. To guarantee that the specified functions and proposed architecture govern the system behavior, H/sub infinity / control theory and model reduction techniques are used. Several experiments were conducted to verify the theoretical derivations. This control method is unique, because it does not require any transfer of either position or velocity information between the master robot and the slave robot; it only requires the transfer of forces. Although this property leads to a wider communication bandwidth between the master and slave robots, the entire system may still suffer from a positional error buildup between the master robot and slave robot. >

Hybrid Control of the Berkeley Lower Extremity Exoskeleton (BLEEX)

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.

Exoskeletons for human power augmentation

The first load-bearing and energetically autonomous exoskeleton, called the Berkeley Lower Extremity Exoskeleton (BLEEX) walks at the average speed of two miles per hour while carrying 75 pounds of load. The project, funded in 2000 by the Defense Advanced Research Project Agency (DARPA) tackled four fundamental technologies: the exoskeleton architectural design, a control algorithm, a body LAN to host the control algorithm, and an on-board power unit to power the actuators, sensors and the computers. This article gives an overview of the BLEEX project.

The development and testing of a human machine interface for a mobile medical exoskeleton

Current advancements in exoskeleton robotics allow those with mobility disorders to walk again. The user conveys his or her desired motion to the exoskeleton using a Human Machine Interface (HMI). This allows the users to stand up, walk, and sit down independently. Existing HMIs require unnatural motions that inhibit the gait. The HMI developed here uses natural gestures while ensuring the safety of the user. This method utilizes a unique sensor suite and a finite state automaton to allow a spinal cord injury patient to easily use an exoskeleton for mobility.

Design of an electrically actuated lower extremity exoskeleton

Human exoskeletons add the strength and endurance of robotics to a humans innate intellect and adaptability to help people transport heavy loads over rough, unpredictable terrain. The Berkeley lower extremity exoskeleton (BLEEX) is the first human exoskeleton that was successfully demonstrated to walk energetically autonomous while supporting its own weight plus an external payload. This paper details the design of the electric motor actuation for BLEEX and compares it to the previously designed hydraulic actuation scheme. Clinical gait analysis data was used to approximate the torques, angles and powers required at the exoskeletons leg joints. Appropriately sized motors and gearing are selected, and put through a thorough power analysis. The compact electric joint design is described and the final electric joint performance is compared with BLEEXs previous hydraulic actuation. Overall, the electric actuation scheme is about twice as efficient and twice as heavy as the hydraulic actuation.

That Which Does Not Stabilize, Will Only Make Us Stronger

Many places in the world are too rugged or enclosed for vehicles to access. Even today, material transport to such areas is limited to manual labor and beasts of burden. Modern advancements in wearable robotics may make those methods obsolete. Lower extremity exoskeletons seek to supplement the intelligence and sensory systems of a human with the significant strength and endurance of a pair of wearable robotic legs that support a payload. This article first outlines the use of Clinical Gait Analysis data as the framework for the design of such a system at UC Berkeley. This data is used to design the exoskeleton degrees of freedom and size its actuators. It will then give an overview of one of the control schemes implemented on the BLEEX. The control algorithm described here increases the system closed loop sensitivity to its wearer’s forces and torques without any measurement from the wearer (such as force, position, or electromyogram signal). The control algorithm uses the inverse dynamics of the exoskeleton, scaled by a number smaller than unity, as a positive feedback controller. This controller almost destabilizes the system since it leads to an overall loop gain slightly smaller than unity and results in a large sensitivity to all wearer’s forces and torques thereby allowing the exoskeleton to shadow its wearer.

Control and system identification for the Berkeley lower extremity exoskeleton (BLEEX)

The Berkeley lower extremity exoskeleton (BLEEX) is an autonomous robotic device whose function is to increase the strength and endurance of a human pilot. In order to achieve an exoskeleton controller which reacts compliantly to external forces, an accurate model of the dynamics of the system is required. In this report, a series of system identification experiments was designed and carried out for BLEEX. As well as determining the mass and inertia properties of the segments of the legs, various non-ideal elements, such as friction, stiffness and damping forces, are identified. The resulting dynamic model is found to be significantly more accurate than the original model predicted from the designs of the robot.

Control scheme and networked control architecture for the Berkeley lower extremity exoskeleton (BLEEX)

The Berkeley lower extremity exoskeleton (BLEEX) is a load-carrying and energetically autonomous human exoskeleton that, in this first generation prototype, carries up to a 34 kg (75 Ib) payload for the pilot and allows the pilot to walk at up to 1.3 m/s (2.9 mph). This article focuses on the human-in-the-loop control scheme and the novel ring-based networked control architecture (ExoNET) that together enable BLEEX to support payload while safely moving in concert with the human pilot. The BLEEX sensitivity amplification control algorithm proposed here increases the closed loop system sensitivity to its wearers forces and torques without any measurement from the wearer (such as force, position, or electromyogram signal). The tradeoffs between not having sensors to measure human variables, the need for dynamic model accuracy, and robustness to parameter uncertainty are described. ExoNET provides the physical network on which the BLEEX control algorithm runs. The ExoNET control network guarantees strict determinism, optimized data transfer for small data sizes, and flexibility in configuration. Its features and application on BLEEX are described