Modeling and Parameter Identification of Harmonic Drive Systems

Abstract

The unique performance features of harmonic drives, such as high gear ratios and high torque capacities in a compact geometry, justify their widespread industrial application. However, harmonic drive can exhibit surprisingly more complex dynamic behavior than conventional gear transmission. In this paper a systematic way to capture and rationalize the dynamic behavior of the harmonic drive systems is developed. Simple and accurate models for compliance, hysteresis, and friction are proposed, and the model parameters are estimated using least-squares approximation for linear and nonlinear regression models. A statistical measure of variation is defined, by which the reliability of the estimated parameter for different operating condition, as well as the accuracy and integrity of the proposed model is quantified. By these means, it is shown that a linear stiffness model best captures the behavior of the system when combined with a good model for hysteresis. Moreover, the frictional losses of harmonic drive are modeled at both low and high velocities. The model performance is assessed by comparing simulations with the experimental results on two different harmonic drives. Finally, the significance of individual components of the nonlinear model is assessed by a parameter sensitivity study using simulations.

A Survey on the Control of Flexible Joint Robots

“…Seyfferth, et al, also provides a nonlinear model for harmonic drive, mostly concentrating on the hysteresis behavior of the compliance [47]. Taghirad and Belanger have re-examined the nonlinear dynamical models for harmonic drives in [48], and proposed a considerably simpler model for the system, in which the stiffness is found to be linear but the structural damping of the system is nonlinear. Using a frequency domain identification method, they proposed a completely linear model for the system in [49], encapsulating the nonlinear behavior of the structural damping and friction of the system into a multiplicative uncertainty model.…”

Strength Analysis and Reliability Evaluation for Speed Reducers

“…An often used reducer for high reduction ratio and small volume is harmonic drive (HD). The HD is designed using a Flexible spline which possesses the properties of small backlash, high transmission accuracy, and large reduction ratio so that it is extensively used in robotic devices [1]. The existed problems of the HD are their rigidity due to the flexible design of the decelerated gear rings [2].…”

Modeling of Elastic Robot Joints with Nonlinear Damping and Hysteresis

“…by Ferretti et al (2004), Zollo et al (2005), Albu-Schaffer et al (2008) and migrating towards the more complex nonlinear approaches as proposed e.g. by Taghirad & Bélanger (1998), Dhaouadi et al (2003), Tjahjowidodo et al (2006), particularly in context of harmonic drive gear transmissions. Here it is important at which level of detail the robot joint transmission could be described.…”

“…However, a specific mechanical assembly 15 www.intechopen.com provides the harmonic drive gears with additional elasticities which are strongly coupled with frictional effects. A structure-oriented dissipative model of the harmonic drive torque transmission was proposed by Taghirad & Bélanger (1998). The model composes multiple component-related frictional elements and an additional structural damping attributed to the flexspline.…”