A new hydraulic brake utilizing a self-energizing effect is developed at the Institute for Fluid Power Drives and Controls (IFAS). In addition to a conventional hydraulic braking actuator, it features a supporting cylinder conducting the braking forces into the vehicle undercarriage. The braking force pressurizes the fluid in the supporting cylinder and is the power source for pressure control of the actuator. The new brake needs no external hydraulic power supply. The only input is an electrical braking force reference signal from a superior control unit. One major advantage of the SEHB concept is the direct control of the actual braking torque despite friction coefficient changes. The prototype design, presented in this paper, is done in two phases. The first prototype is based on an automotive brake caliper. It is set up to gain practical experience about the hydraulic self-energisation and to prepare the laboratory automation environment. Active retraction is required for train brakes though, which cannot be done with automotive brakes. The second prototype therefore features a differential double acting braking cylinder with a pre-stressed spring for fail safe braking. A mechanical design systematics is presented which helps to map requirement specifications originating from a particular application to implementation in a structural design. The promising dynamic behavior of SEHB based on simulation results is presented.
The self-energizing-electro-hydraulic brake is a new energy saving electro-hydraulic brake which offers the unique possibility of direct brake torque control. Its open loop characteristics are unstable, demanding for a feedback control in normal operation. This paper describes the analytical design of a nonlinear input-output-linearizing controller for the brake and discusses the robustness of that control. The control task of the brake is stated as tracking the reference signal and reaching an aperiodic time response of the brake torque. In order to design the control a simplified model of 4 th order is used. The coordinate's transformation and input-output linearization are applied to the simplified model. The control signal for the model is constructed via the pole placement method. The nonlinear controller shows good performance in nonlinear system simulation.
In pressure control applications, servo-valves or variable displacement pumps are used to meter the flow into a supply line or a chamber with relatively constant capacity, thereby controlling its pressure under the influence of disturbances such as flows in and out of the controlled volume. For most applications proportional integral derivative (PID) controllers are suited and widely used in research and practice. However, tuning of PID parameters for pressure control is usually done by trial and error method due to the lack of applicable tuning rules for this case. The paper examines the dynamics of valve controlled pressure applications and proposes a set of effective but simple PID feedback gain formulas. They can be implemented by practitioners on the basis of data that in most cases is available from plant drawings and the valve data sheet. The tuning rule's parameters are based on a straight forward frequency response design. They yield swift and robust performance in simulation and experiment.
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