Sliding mode control of position commanded robot manipulators (original) (raw)
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Proceedings of the 18th IFAC World Congress, 2011
In this work, the joint position tracking control problem of industrial robots is tackled. To cope with the model uncertainties and external disturbances affecting the robot, the Inverse Dynamic Controller (IDC) is combined with an approach based on higher order Sliding Mode Control (SMC) technique. We make use, in particular, of the so-called "Twisting" Second Order Sliding Mode Controller. Higher order SMC techniques transfer the inherent discontinuities to the time derivative of the input torque and this allows to obtain a continuous profile for the input torque, which is computed through integration of an appropriate discontinuous switching signal. Despite the chattering phenomenon is strongly attenuated, some residual problems (vibration and acustical noise) are still observed during the experimental implementation of such an approach in its standard formulation. To improve the system performance we suggest in this work an adaptation mechanism to adjust on-line the authority of the SMC. The logic is driven by a "sliding-mode indicator" that detects, on line, the occurrence of a sliding mode behaviour and uses this information for adaptation purposes. When large and fast control activity is demanded (e.g. to track fast reference trajectories) the adaptation unit reacts by automatically increasing the control authority of the SMC. On the other hand when small control authority is sufficient the control magnitude is lowered. Such a bidirectional adaptation logic significantly reduces the chattering. The proposed technique is theoretically analyzed and experimentally tested, and the results of comparative experiments are discussed in the paper.
sliding mode control of robot manipulator
Design a nonlinear controller for second order nonlinear uncertain dynamical systems is one of the most important challenging works. This course focuses on the design, implementation and analysis of a chattering free sliding mode controller for highly nonlinear dynamic PUMA robot manipulator and compare to computed torque controller, in presence of uncertainties. These simulation models are developed as a part of a software laboratory to support and enhance graduate/undergraduate robotics courses, nonlinear control courses and MATLAB/SIMULINK courses at research and development company (SSP Co.) research center, Shiraz, Iran.
International Journal of Industrial Electronics, Control and Optimization (IECO), 2020
In this paper, a novel model-free control scheme is developed to enhance the tracking performance of robotic systems based on an adaptive dynamic sliding mode control and voltage control strategy. In the voltage control strategy, actuator dynamics have not been excluded. In other words, instead of the applied torques to the robot joints, motor voltages are computed by the control law. First, a dynamic sliding mode control is designed for the robotic system. Then, to enhance the tracking performance of the system, an adaptive mechanism is developed and integrated with the dynamic sliding mode control. Since the lumped uncertainty is unknown in practical applications, the uncertainty upper bound is necessary in the design of the dynamic sliding mode controller. Hence, the lumped uncertainty is estimated by an adaptive law. The stability of the closed-loop system is proved based on the Lyapunov stability theorem. The simulation results demonstrate the superior performance of the proposed adaptive dynamic sliding mode control strategy.
Real-time implementation of regressor-based sliding mode control algorithm for robotic manipulators
IEEE Transactions on Industrial Electronics, 1993
A regressor-based variable structure control scheme has been developed for the trajectory control of robot manipulators in the presence of disturbances, parameter variations, and unmodeled dynamics. The method is based on the regressor structure given by Slotine and Li, 131, without parameter adaptation. This avoids the requirement of persistency of excitation, and the convergence of the overall transient is exponential. The method is robust against a class of state-dependent uncertainties, which may result, for example, from unmodeled dynamics. The problem of chattering is solved by the smoothing control law. It is shown that the closed-loop system is globally ultimately bounded with respect to a set around the origin, which can be made arbitrarily small. To illustrate the feasibility of this controller, it was implemented using a Motorola M68000 microprocessor on a two-link revolute joint manipulator subjected to a variable payload. Experimental results confirm the validity of accurate tracking capability and the robust performance.
Sliding Mode Control Based on Synthesis of Approximating State Feedback for Robotic Manipulator
International Journal on Electrical Engineering and Informatics, 2017
In this paper, three paradigms are used to deal with a robot manipulator control problem. These paradigms are feedback linearization method, approximating control by Taylor truncation, and sliding mode approach. Robotic manipulator is highly nonlinear, highly time-varying, and highly coupled. In robotic manipulator there are many uncertainties such as dynamic parameters (eg., inertia and payload conditions), dynamical effects (e.g., complex nonlinear frictions), and unmodeled dynamics. The classical linear controllers have many difficulties in treating these behaviors. To overcome this problem, sliding mode control (SMC) has been widely used as one of the precise and robust algorithms. Application of traditional SMC in nonlinear system uses exact feedback linearization. Geometric differential theory is used to develop exact linearization transformation of nonlinear dynamical system, by using nonlinear cancellation and state variable transformation. Hence, the controller can be synthesized by using the standard sliding mode for linear system. The main weak point of the exact linearization is that its implementation is difficult. This study presents a synthesis SMC based on approximating state feedback for robotic manipulator control system. This approximating state feedback is derived from exact feedback linearization. Based on approximating state feedback, sliding mode controller is derived. The closed loop stability is evaluated by using the Lyapunov like theory.
Review of Sliding Mode Control of Robotic Manipulator
Abstract: Control of robotic systems is vital due to wide range of their applications because this system is multi-input multi-output, nonlinear and uncertainty. Consequently, it is difficult to design accurately mathematical models for multiple degrees of freedoms robot manipulator. Therefore, strong mathematical tools used in new control methodologies to design a controller with acceptable performance. As it is obvious stability is the minimum requirement in any control system, however the proof of stability is not trivial especially in the case of nonlinear systems. One of the best nonlinear robust to control of robot manipulator is sliding mode controller. A review of sliding mode controller for robot manipulator will be investigated in this paper.
Second order sliding mode control for robot arms with time base generators for finite-time tracking
2001
A novel chattering-free dynamic sliding mode controller for a class of uncertain mechanical systems is proposed in order to account globally for a time-varying sliding regime for all time and for any initial condition. The new sliding surface, parametrized by a time base generator, plays the role of moving, and rotating continuously the nominal sliding surface, while shifting is done through a known, state-independent, vanishing vector to eliminate the reaching phase for any initial condition, a weaker assumption in comparison to some moving sliding surface designs. In this way, the closed-loop system yields finite-time convergence of tracking errors, whose convergence time can be fixed independently of initial conditions, in contrast to terminal sliding mode wherein convergence time depends on initial conditions. To implement the controller, the upper bound of the derivative of the sliding surface is required, a weaker assumption in contrast to some dynamic sliding mode controllers. The performance of the closed-loop system is visualized through simulation.
Control of Lightweight Manipulators Based on Sliding Mode Technique
Advances in Robot Manipulators, 2010
This chapter focuses on the dynamic control issues of lightweight robots as well as flexible joint robots. The goal is to increase the bandwidth and the accuracy of the trajectory tracking control. Besides the joint flexibility, the control design considers the dynamics of the electric motor in AC-form i.e. the three phase permanent magnet synchronous motor (PMSM). The final system model is a fifth order non-linear system. Based on the theory of integral sliding mode control a robust control approach for the trajectory tracking control of rigid-body robots is presented at first. This control approach has pole-placement capability despite system uncertainties. The controller is then used as the outer position controller for the control of flexible joint robots. To handle the joint flexibility, singular perturbation approach is employed, resulting in reference currents for the inner current control loop of joint motors. For the current control, sliding mode PWM technique is used to overcome the disadvantages of conventional open-loop PWM. The developed control algorithms are simple enough for practical implementation and verified by simulation studies based on a dynamic model consisting of a two-link flexible joint robot with two joint motors.
Second order sliding mode motion control of rigid robot manipulators
2007
This paper presents a control strategy for robot manipulators, based on the coupling of the inverse dynamics method with the so-called second order sliding mode control approach. The motivation for using sliding mode control in robotics mainly relies on its appreciable features, such as design simplicity and robustness. Yet, the chattering effect, typical of the conventional sliding mode control, can be destructive. In this paper, this problem is suitably circumvented by adopting a second order sliding mode control approach characterized by a continuous control law. To design the inverse dynamics part of the proposed controller, a suitable dynamical model of the system has been formulated, and its parameters have been accurately identified. The proposed inverse dynamics-based second order sliding mode controller has been experimentally tested on a COMAU SMART3-S2 industrial manipulator, demonstrating the tracking properties and the good performances of the controlled system.
Discrete-time sliding mode control of a direct-drive robot manipulator
2004 43rd IEEE Conference on Decision and Control (CDC) (IEEE Cat. No.04CH37601), 2004
This paper investigates the application of a recently introduced discrete-time sliding mode algorithm in robot motion control. The algorithm was developed to ensure chattering-free discrete-time sliding mode control in finite time. Robustness against disturbances and modeling errors are the additional merits of this algorithm. Here, the algorithm is adapted for the robot motion control problem, and it is used to design feedback controllers of a benchmark directdrive robot. Theory and experiments confirm the applicability of the algorithm. However, they also reveal restrictions in controller tuning, that may result in undesirable amplification of noise and in excitation of parasitic dynamics.