Abstract
Abstract. Continuum manipulators are widely used in minimally invasive surgical robot systems (MISRS) because of their flexibility and compliance, while their modelling and control are relatively difficult and complex. This paper proposes an improved hysteresis model of a notched continuum manipulator based on the classical Bouc–Wen model, which can reduce errors and increase the accuracy of the kinematic-mechanics coupled model. Then parameters are identified by the mean of genetic algorithm (GA). Hysteresis phenomenon of the mentioned manipulator is actually caused by many factors such as the hysteresis property of Hyperelastic Nitinol Alloy (HNA), the elastic deformation of tendon and the friction between the tendon and the tube. The results of both static and dynamic experiments show that the introduced hysteresis model can eliminate the positional difference between forward and reverse bending processes, and thus improve the forecast precision of deformation during motion. This model can also be used to compensate modelling errors caused by hysteresis of other similar systems.
Highlights
Continuum robots, different from conventional discrete joints robots, do not contain rigid links and identifiably rotational joints, whose deformation bases on intrinsic elastic and compliant character (Robinson and Davies, 1999)
This section reviews the previous contributions which plays a fundamental role in the subsequent research, including the overall structure, mechanics model and kinematics model of a single notched ring (SNR) unit and the integrated manipulator (Du et al, 2015b)
The overall structure is made of Hyperelastic Nitinol Alloy (HNA) tube on which several V-shape cuts are processed by lowspeed wire cut electrical discharge machining (LS-WEDM), and two tendons are fixed at the tip of the manipulator to transmit driving force
Summary
Different from conventional discrete joints robots, do not contain rigid links and identifiably rotational joints, whose deformation bases on intrinsic elastic and compliant character (Robinson and Davies, 1999). Kato et al (2016) took hysteresis of a tendon-driven continuum robot for neuroendoscopy into account by adding friction coefficient into their model instead of using fitting parameters, and this research only worked out the hysteresis caused by the friction. Consideration of hysteresis problem of the notched continuum manipulator driven by the tendon during modelling is important to improve the modelling accuracy, and the designed hysteresis model and parameter identification method in this paper is effective.
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