Ronita Saha

Designing low-chattering sliding mode controller for an electrohydraulic system

Sliding mode controllers of first and second orders have been designed for linear motion tracking for an eletrohydraulic actuation system having deadband and other nonlinear features like cylinder stiction, hysterisis and Stribeck characteristics. An input linearized structure has been developed to formulate sliding mode controllers, or SMC, of orders 1 and 2 for the nonlinear system. The applied SMC is coupled with a simple integral compensator for attenuating both the chatter of the input signal and any steady state error of the output. Real-time experiments have been carried out that show the first-order controller as better above 1.4Hz tracking and the second-order controller as better below 1.4Hz.

Analysis of 6-DOF motion with PI controller in electrohydraulic stewart platform

A Stewart platform that is a 6-DOF parallel manipulator with a moveable frame for three linear and three angular motions has been designed with electrohydraulic actuation for achieving maneuverability of heavy load. A popular application is the motion simulator for an aircraft or a ship that could be used for training by generating specific motions within the confine of a laboratory. The main contribution of this work is the design and realization of a high-precision simulator with low-cost proportional valves using a simple PI controller for achieving basic motions. A pose-feedback controller has been conceived for the system constructed on the basis of the feedback of the leg lengths and a linearized inverse kinematic model about the neutral position. A number of real-time experiments have shown the design to be quite satisfactory.

Designing sliding mode with integral control for angular rotation of a link by linear electrohydraulic actuation

Precise control of link rotation through linear actuation system invokes considerable research interest in the emerging field of electrohydraulic robotics for negotiating heavy external loads. Major challenges emerge for achieving precise control despite wide ranges of demands and disturbances overcoming severe nonlinearities of an electrohydraulic system. A set up has been commissioned to generate angular motion of a link by linear eletrohydraulic actuator. An advanced integral control has been developed in combination with first-order sliding-mode control, or 1-SMC, which is withdrawn for small value of the sliding variable to avoid inherent chattering due to SMC. The controller has been executed in the joint space of linear actuation of a cylinder-piston arrangement through kinematic transformation of the output space of rotation of a link. Most notable outcome of the proposed design is control with low chattering of the control voltage to the valve and its superiority over the conventional PI has been attributed in this study.

Adaptive PID control for angular motion tracking by linear Electrohydraulic Actuation

Angular motion tracking of a link mechanism has been accomplished through a high-power linear actuation with multiple nonlinearities in an electrohydraulic system. For achieving precise control regardless of wide variations in demands and disturbances, an adaptive PID controller has been formulated. The convergence of the controller has been established by suitable Lyapunov function definition. Real-time experiments have been carried out to confirm the acceptance of the controller design. In comparison to a non-adaptive PID controller, the designed adaptive PID has yielded superior response. The experiments pertain to demands up to 9.5Hz with 8MPa relief valve setting.