The effect of mechanism design on the performance of a quadruped walking machine

The objective of this paper is to investigate the effect of mechanism design on the performance of a quadruped walking machine. For studying the effect of mechanism design on the performance of a quadruped walking machine, four designs with different crank and leg arrangements are proposed and analyzed. The performance of the walking machine, including the stance leg sequence, foot trajectory, pitch angle, and dynamic response of the quadruped walking machine are investigated and compared with the existing design. The results show that the phrase angle between front and rear legs on the same side should be 0° or 90° and the one between the legs on the different sides should be 180°. And, the design with the front and rear legs bent in the same direction has better performance in dynamic responses. The results of this study can serve as a reference for future design and optimization of quadruped walking machines

System Design of a Cheetah Robot Toward Ultra-high Speed

High-speed legged locomotion pushes the limits of the most challenging problems of design and development of the mechanism, also the control and the perception method. The cheetah is an existence proof of concept of what we imitate for high-speed running, and provides us lots of inspiration on design. In this paper, a new model of a cheetah-like robot is developed using anatomical analysis and design. Inspired by a biological neural mechanism, we propose a novel control method for controlling the muscles' flexion and extension, and simulations demonstrate good biological properties and leg's trajectory. Next, a cheetah robot prototype is designed and assembled with pneumatic muscles, a musculoskeletal structure, an antagonistic muscle arrangement and a J-type cushioning foot. Finally, experiments of the robot legs swing and kick ground tests demonstrate its natural manner and validate the design of the robot. In the future, we will test the bounding behaviour of a real legged system

Adaptive foot design for small quadruped robots

Biologically inspired robots that are used for research of the animal and the technological realm become more and more refined. Control schemes for sensor-less and sensorized robots were developed, are able to handle torque control and sometimes even adapt to a changing task set. Further mechanics and electronics have evolved and take part in more reliable and robust bio-inspired robots. Robots reproduce animal structures or use bio-mechanical principles to excel in a specific task. Never the less, during this evolution of robots the feet were often oversimplified compared to their animal counterparts. Our current work centers around the foot as a bio-mechanically complex but extremely important end-effector

Kinematic primitives for walking and trotting gaits of a quadruped robot with compliant legs

In this work we research the role of body dynamics in the complexity of kinematic patterns in a quadruped robot with compliant legs. Two gait patterns, lateral sequence walk and trot, along with leg length control patterns of different complexity were implemented in a modular, feed-forward locomotion controller. The controller was tested on a small, quadruped robot with compliant, segmented leg design, and led to self-stable and self-stabilizing robot locomotion. In-air stepping and on-ground locomotion leg kinematics were recorded, and the number and shapes of motion primitives accounting for 95% of the variance of kinematic leg data were extracted. This revealed that kinematic patterns resulting from feed-forward control had a lower complexity (in-air stepping, 2 to 3 primitives) than kinematic patterns from on-ground locomotion (4 primitives), although both experiments applied identical motor patterns. The complexity of on-ground kinematic patterns had increased, through ground contact and mechanical entrainment. The complexity of observed kinematic on-ground data matches those reported from level-ground locomotion data of legged animals. Results indicate that a very low complexity of modular, rhythmic, feed-forward motor control is sufficient for level-ground locomotion in combination with passive compliant legged hardware

Investigating balance control of a hopping bipedal robot

Legged robots are dynamic moving machines that are potentially able to traverse through rough terrain which is inaccessible for wheeled or tracked vehicles. For bipedal robots, balancing control while hopping/running is challenging, especially when the foot contact area is small. Servo hydraulics is highly suitable for robot leg actuation due to its high power density and good power-to weight ratio. This paper presents a controller for a hydraulically actuated bipedal robot, the Bath Bipedal Hopper (BBH). The controller follows the well-established structure of the ‘Three-part’ control algorithm. The three parts are: hopping height control; longitudinal velocity control by changing the leg angle during the flight phase to place the foot in the desired position; and body attitude correction during the stance phase. Simulation results from a detailed non-linear model indicate that this controller can successfully balance the hydraulic robot while hopping with different longitudinal velocities