In this study, design method of a walking robot is suggested by providing design conditions and systematic design procedure both for static gait and for dynamic gait. Design goal is based on the design of walking robot of 1.0m height and about 70kg weight. Designed walking robot KAISER II showed overall configuration 1.4m long, 1.0m high and weighed about 80kg including payload. It could walk as fast as 0.1m/s in level ground and climb 50% grade stairs.
Design procedure of walking robot suggested in this study includes specification of design goal and design condition, selecting leg mechanism, selecting motor and transmission system, deciding walking volume detail design, analysis of walking robot and finally fabrication. Important performances in the design are mobility walking velocity energy efficiency and payload of walking robot.
Mobility energy efficiency, fabrication, simple inverse kinematics and deflection by body weight are used as design conditions of leg mechanism. The conditions are used to evaluate walking robot and select leg mechanism. Pantograph mechanism among seven bar mechanisms of two DOF is selected and developed for three dimensional motion in the respect of design conditions. Detail design of pantograph is accomplished with the walking volume, walking speed and deflection that determines mobility of walking robot. In selecting motors and transmission system, it is found that the walking robot can walk faster with the more powerful motors. Validity of the suggested design procedure has been checked through the design of quadruped walking robot KAISER II. As the results, pantograph of large magnification ratio is proved to be a successful mechanism as a leg of walking robot. It is also found that deflection of leg as much as 0.5% of body height is moderate both for weight of leg and walking speed.
To improve walking speed of the robot, dynamic gait is also studied. For this purpose, the dynamic gait of quadruped walking robot is numerically simulated with three dimensional dynamic model. A gait pattern named ""Simple Trot"" is adapted as a suitable gait pattern for the walking robot among several gait patterns that the vertebrate animals take. Conditions such as symmetric gait, gait of duty factor between 0.5 and 0.75, and regular gait are considered for the gait pattern to simplify the walking strategy. The feasibility conditions for the successful gait are suggested to be periodic, roll over the diagonal support line, be ready for soft town down of swing leg and maintain balance of body during statically stable phase.
Through computer simulation of dynamic gait, it is found that walking velocity limits of the walking robot is proportional to stroke and square root of body height. The initial angular momentum required just before the inverted pendulum phase is proved to be proportional to square of stroke angle of diagonal support line and inverse of walking velocity by numerical simulation. The range of feasible initial angular velocity of body depends on phase difference between legs that forms diagonal support line. The most wide range of initial angular velocity are obtained when $\phi = (\beta -0.5)$.
