Development of a Quadruped Rotary Piezoelectric Platform With Ultra-Low Speed Fluctuations

Piezoelectric platforms have wide applications in the fields of aerospace, biomedicine, and precision instruments due to their nanoscale resolution and fast response. However, the existing piezoelectric platforms suffer from speed fluctuations caused by intermittent stepping actuation principle and unstable transition. To solve this problem, a quadruped rotary piezoelectric platform (QRPP) using multileg continuous alternating cooperative stepping actuation is proposed. The QRPP achieves a smooth transition of driving force between phases and near-uniform motion by the coordinated operations of the four driving feet. Besides, an inverse kinematics feedforward compensation method (IKFCM) is proposed to further reduce the speed fluctuations induced by the stiffness variation and preload imbalance among the legs in practical application, which can compensate the voltage signals to excite the smooth angular displacement trajectory of QRPP. The theoretical model of IKFCM is established. Experimental results demonstrate that the QRPP with IKFCM exhibits positive effect against speed fluctuations under varying excitation voltages, operating frequencies, external loads, and output torques. The angular speed fluctuations from -6.44 to +6.60 nrad/s is achieved. In addition, an angular displacement resolution of 61 nrad, a load capacity of 2.5 kg, and a maximum output torque of 1.813 N·m are measured.