Design and Development of a Rayleigh Oscillator-Based Reference Angle Generator for Motion Control of Smart Prosthetic Knees

Abstract

In order to synchronize the motions of the above-knee amputee's limbs and smart prosthetic knee in practical applications, the principle of a Rayleigh oscillator-based reference angle generator (RORAG) for the motion control of smart prosthetic knees is proposed. The central pattern generator (CPG) model of the lower limb in this paper uses a pair of phase-coupling Rayleigh oscillators to imitate the human's lower limb's biological CPG, where the used Rayleigh oscillators are improved to exactly represent the motion characteristics of the lower limb. A frequency control method for the CPG model is proposed to synchronize the thigh reference angle, which is generated by the lower limb's CPG model, with the swing angle of the above-knee amputee's residual thigh. The RORAG model is developed by using the real-time simulation system. An experimental system is developed to verify the performance of the RORAG model in two terms of the curve shape and motion synchronization. Further, in order to estimate the application value of the proposed RORAG model in two terms of the real-time and accuracy, a bio-guided motion platform system is developed and fabricated. On this motion platform system, the RORAG model is used to control a prosthetic knee prototype. The experimental results show that the developed RORAG model can imitate the subject's knee joint's swing angle accurately in real time. Therefore, the proposed RORAG is effective in practical applications.

Keywords

• Motion characteristics
• reference angle generator
• prosthetic knees
• Rayleigh oscillator