Abstract
This paper investigates the model-based nonlinear control of a class of soft continuum pneumatic manipulators that bend due to pressurization of their internal chambers and that operate in the presence of disturbances. A port-Hamiltonian formulation is employed to describe the closed loop system dynamics, which includes the pressure dynamics of the pneumatic actuation, and new nonlinear control laws are constructed with an energy-based approach. In particular, a multi-step design procedure is outlined for soft continuum manipulators operating on a plane and in 3D space. The resulting nonlinear control laws are combined with adaptive observers to compensate the effect of unknown disturbances and model uncertainties. Stability conditions are investigated with a Lyapunov approach, and the effect of the tuning parameters is discussed. For comparison purposes, a different control law constructed with a backstepping procedure is also presented. The effectiveness of the control strategy is demonstrated with simulations and with experiments on a prototype. To this end, a needle valve operated by a servo motor is employed instead of more sophisticated digital pressure regulators. The proposed controllers effectively regulate the tip rotation of the prototype, while preventing vibrations and compensating the effects of disturbances, and demonstrate improved performance compared to the backstepping alternative and to a PID algorithm.
Highlights
Soft continuum manipulators have been attracting increasing attention in the research community because, unlike conventional rigid mechanisms, they can interact safely with uncertain and delicate objects [34]
We investigate the energy-based control of soft continuum pneumatic manipulators that can bend on any plane due to internal pressurization
This paper presented a new energy-based control strategy for a class of soft continuum pneumatic manipulators that can bend on any plane
Summary
Soft continuum manipulators have been attracting increasing attention in the research community because, unlike conventional rigid mechanisms, they can interact safely with uncertain and delicate objects [34]. This property is a consequence of the structural compliance of soft actuators and makes them ideally suited for several applications, including surgery and rehabilitation [33]. Not all degrees of freedom (DOFs) in soft continuum manipulators are actuated. This attribute, together with the presence of unknown external forces, which are common in realworld applications, makes the control of soft continuum actuators and manipulators a challenging task [39]
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