Foot contact force of walk gait for a quadruped robot

Central Pattern Generator (CPG) can be used to generate rhythmic control signals for quadruped locomotion, such as walk, trot, and gallop gait. The walk gait is a statically stable quadruped gait, and suitable for enhancing the robustness of robots. However, as a result of lacking consideration of dynamics characteristics of robots, the swing phase of control signals generated by CPG may be not consistent with the actual phase of the quadruped limb. For example, there is a fact in walk gait that the control signal generated by CPG is in swing phase, while the quadruped limb is still in contact with the ground. So we attach the force sensor on the quadruped foot to detect the real-time foot contact force when a quadruped robot walks on the ground substrate, and the actual contact-lift state of the limb. Using the foot contact force information, we accurately obtain the difference between the theoretical-actual swing phase. Moreover, we discuss that foot-substrate contact force can be used to distinguish the ground substrate with different properties such as friction coefficient. Experiment results show the possibility to utilize force sensor information for ground substrate recognition and classification.