Identification of the Elasticity Coefficient of Manipulator Rotary Joint Using an Accelerometer and Angular Velocity Sensor

The article proposes a method for identifying the torsional stiffness coefficient of a manipulator's rotary joint using a MEMS Inertial Measurement Unit (accelerometer and angular velocity sensor). The method is based on describing the dynamics of a joint with an unknown stiffness coefficient using a transfer function with known input and output signals (motor rotation angle and link rotation angle, respectively). The transfer function input signal is read from the motor encoder, and the output signal is reconstructed based on data from the Inertial Measurement Unit. When assigning harmonic signals with different frequencies to the drive, the amplitudes of the input and output signals are measured, and the amplitude-frequency characteristic of the transfer function is constructed based on the obtained data, from which its time constants are calculated. The time constants depend on the mechanical characteristics of the system, including the torsional stiffness coefficient, which is calculated based on the time constants. The method, unlike existing ones, does not require either bulky equipment for applying external forces to the manipulator or expensive measuring systems for measuring displacements in space. The results of mathematical modeling confirm the efficiency of the method.