Indirect measurement method of ultrasonic bone cutting force based on anti-node vibration displacement

Abstract

The measurement method of ultrasonic bone cutting force is an urgent problem to be solved in the application of ultrasonic osteotome in robot assisted orthopaedic surgery. It is of great significance to realize bone layer perception and cutting force control in the process of surgery. In this paper, an indirect measurement method of ultrasonic bone cutting force based on anti-node vibration displacement is proposed for the first time. Firstly, a one-dimensional numerical model for the interaction between ultrasonic osteotome and bone tissue is established. The model consists of two modules. The first module is the electromechanical model of ultrasonic osteotome, including piezoelectric transducer model and stepped horn model. The second module is the load model simulating ultrasonic bone cutting, which can be expressed by the Kelvin-Voigt model. The influence of load on the vibration characteristics of ultrasonic osteotome was studied by a one-dimensional numerical model. A full factorial design of experiment is used to collect the necessary data for developing and validating the models. Then, the indirect measurement model of ultrasonic bone cutting force is developed by using grey wolf optimized BP (GWO-BP) neural network algorithm. Taking the effective value x1rms and vibration frequency fx1 of anti-node vibration displacement as inputs, the effective value Frms of cutting force is output. It is found that the predicted effective value of cutting force is in good agreement with the corresponding numerical calculated effective value of cutting force. Finally, the continuous system of ultrasonic osteotome and bone tissue interaction is simulated by finite element method, the discrete system of ultrasonic osteotome and bone tissue interaction is simulated by physical method, and the experimental platform for indirect measurement of cutting force is built. The corresponding relationship between cutting force and anti-node vibration displacement is illustrated, which further verifies the effectiveness and feasibility of the indirect measurement method of ultrasonic bone cutting force based on anti-node vibration displacement.