Abstract
A non-linear optimal (H-infinity) control approach is proposed for the dynamic model of multi-degree-of-freedom (DOF) electro-hydraulic robotic manipulators. Control of electro-hydraulic manipulators is a non-trivial problem because of their non-linear and multi-variable dynamics. In this study, the considered robotic system consists of a multi-link robotic manipulator that receives actuation from rotary electro-hydraulic drives. The article's approach relies first on approximate linearisation of the state-space model of the electro-hydraulic manipulator, according to first-order Taylor series expansion and the computation of the related Jacobian matrices. For the approximately linearised model of the manipulator, a stabilising H-infinity feedback controller is designed. To compute the controller's gains, an algebraic Riccati equation is solved at each time-step of the control algorithm. The global stability properties of the control scheme are proven through Lyapunov analysis. The proposed control method retains the advantages of typical optimal control, i.e. fast and accurate tracking of the reference setpoints under moderate variations of the control inputs.
Highlights
Electro-hydraulic actuation systems have been widely used in robotic manipulators, in construction machinery and in aircrafts [1,2,3]
The Riccati equation which has been proposed for computing the feedback gains of the controller is novel, so is the presented global stability proof through Lyapunov analysis. As it will be explained the presented non-linear optimal control method has improved performance when compared against other non-linear control schemes that one can consider for the dynamic model of electrohydraulic robotic manipulators
The article's scientific contribution is outlined as follows: (i) the presented non-linear optimal control method has improved performance when compared against other non-linear control schemes that one can consider for the dynamic model of the multiDOF electro-hydraulic robotic manipulator (such as Lie algebrabased control, differential flatness theory-based control, modelbased predictive control, non-linear model-based predictive control, sliding-mode control, backstepping control, (ii) it achieves fast and accurate tracking of all reference setpoints for the multiDOF electro-hydraulic robotic manipulator under moderate variations of the control inputs, (iii) it minimises the consumption of energy by the multi-DOF electro-hydraulic robotic manipulator's actuators, improving the operational capacity and efficiency in tasks execution for this robotic system
Summary
Electro-hydraulic actuation systems have been widely used in robotic manipulators, in construction machinery and in aircrafts [1,2,3]. The Riccati equation which has been proposed for computing the feedback gains of the controller is novel, so is the presented global stability proof through Lyapunov analysis As it will be explained the presented non-linear optimal control method has improved performance when compared against other non-linear control schemes that one can consider for the dynamic model of electrohydraulic robotic manipulators. The article's scientific contribution is outlined as follows: (i) the presented non-linear optimal control method has improved performance when compared against other non-linear control schemes that one can consider for the dynamic model of the multiDOF electro-hydraulic robotic manipulator (such as Lie algebrabased control, differential flatness theory-based control, modelbased predictive control, non-linear model-based predictive control, sliding-mode control, backstepping control, (ii) it achieves fast and accurate tracking of all reference setpoints for the multiDOF electro-hydraulic robotic manipulator under moderate variations of the control inputs, (iii) it minimises the consumption of energy by the multi-DOF electro-hydraulic robotic manipulator's actuators, improving the operational capacity and efficiency in tasks execution for this robotic system.
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