Easy Estimation of Wheel Lift and Suspension Force for a Novel High-Speed Robot on Rough Terrain

Abstract

In operation of high-speed wheeled robots on rough terrain, it is important to predict or measure the interaction between wheel and ground in order to maintain optimal maneuverability. Therefore, this paper proposes an easy way to estimate wheel lift and suspension force of a high-speed wheeled robot on uneven surfaces. First, a high-speed robot with six wheels with individual steer motors was developed, and with the body of the robot connected to each wheel by semi-active suspensions. In a sensor system, potentiometers, which can measure angle of arms, are mounted at the end of arms and have a critical role in estimating wheel lift and suspension force. A simple dynamic equation of the spring-damper system is used to estimate the suspension force, and the equation is calculated in terms of the suspension displacement by measured angle of arms because the suspension displacement is a function of arm angle in the boundary of the kinematic model of the body–wheel connection. In addition, wheel lift can be estimated using the arm angle. When the robot keeps its initial state without normal force, the arm angle is set as zero point. When the wheels receive the normal force, the link angle is changed to a value higher than zero point. If a wheel does not contact to a ground, then the suspension force goes toward the negative direction as a value. Therefore, if wheel lift happens while driving, the arm angle will follow the zero point or the suspension force will indicate a negative value. The proposed method was validated in ADAM simulations. In addition, the results of the performance were verified through outdoor experiments in an environment with an obstacle using a high-speed robot developed for this purpose.