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

In operation of high-speed wheeled robots on rough terrain, it is significantly 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 highspeed wheeled robot on uneven surfaces. First of all, a high-speed robot which has six wheels with individual steer motors was developed and the body of the robot is 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 it has a critical role to estimate wheel lift and suspension force. A simple dynamic equation of 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 boundary of kinematic model of body-wheel connection. Also, wheel lift can be estimated using the arm angle. When the robot keeps initial state without normal force, the arm angle is set as zero point. When the wheels get the normal force, the link angle is changed to higher value than zero point. And also, 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. And the results of the performance were verified through outdoor experiments in an environment with an obstacle using a developed high-speed robot.