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Electrohydraulic Systems Control
Published in Qin Zhang, Basics of Hydraulic Systems, 2019
Another type of electrohydraulic control actuation is the servo valve, which is also called the servo control valve. Servo control is not a new technology; actually, servo valves were first used in the 1940s. By nature, servo valves are also a type of proportional control valve and can achieve continuous control of the pressure or the flow from zero up to their maximum levels. Such valves commonly use a torque motor (as introduced in Section 3.1.6) in conjunction with sophisticated electronics and closed-loop systems to control the valve position. The feedback controller of the valve can correct the control signal in terms of the feedback signals of the position or force on the actuators (hydraulic cylinders or motors) being controlled, and the servo motor can respond to such corrected control signals promptly. A servo control system can therefore operate with high accuracy, repeatability, and frequency response with very low hysteresis and achieve precise control of the actuator. This type of valve is normally much more expensive to use than solenoid valves but can achieve superior performance. It is commonly used in applications requiring high-precision control over the valve position, such as machine tools.
Servo Feedback Devices and Motor Sensors
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
The primary objective of servo control systems is to not only precisely control the motor speed and position but also achieve the desired motor dynamic response, synchronization, and stability. In servo systems, feedback devices are commonly adopted with other control elements to automatically adjust the output to maintain operating stability, reduce variations, and minimize errors via motion controllers. Fundamentally, a servo system can perform no more accurately than the accuracy of the feedback device. In addition, errors in position or speed can be introduced into the system by the less-than-perfect mechanisms that transfer the motor power to the load [8.1]. In most high-performance servo systems, the position/speed errors are not acceptable.
Robot Controllers
Published in David D. Ardayfio, Fundamentals of Robotics, 2020
From the applications viewpoint, robot controls can be divided into two major categories: nonservo control and servo control. Servo control refers to the type of control in which the manipulator motion is under constant supervision by a computer and requires real-time feedback and analysis of the motion data. Nonservo control is much simpler and requires no feedback. In this chapter, we will describe several types of controllers used in robots, A discussion of some typical systems will illustrate the practical aspects of operation of robot controllers.
A novel adaptive balance-drive mechanism for industrial robots using a series elastic actuator
Published in International Journal of Computer Integrated Manufacturing, 2020
Huashan Feng, Yaping Xu, Dewang Mao
The motion control part of the device consists of an ADVANTECH industrial control computer, a GOOGOLTECH GTS-400-PV-PCI 4-axis motion control card, an analog acquisition and signal processing module, a MOTEC motor servo driver and signal acquisition and control algorithm based on MATLAB. The industrial control computer uses the LVDT sensor to acquire the spring deformation value in real time. It also detects the swing angle of the lever motion via the rotational incremental encoder in the lever joint. The motion control card is used by the computer to send the displacement or torque control signal of the ball screw to the MOTEC motor servo driver, while the actual displacement is read through the motor encoder. A proportional-integral-derivative (PID) closed-loop servo control is utilized in the whole system.
Experimental study on the coupled shear flow behavior of jointed rock samples
Published in European Journal of Environmental and Civil Engineering, 2018
Z. M. Shi, D. Y. Shen, Q. Z. Zhang, M. Peng, Q. D. Li
The servo control unit is characterised by its promptness, high precision and short feedback time. It can maintain a constant normal load (CNL) and measure the normal and tangential stresses of up to 30 MPa with an accuracy of ±1%. It is able to measure the deformation of up to 25 mm with an accuracy of ±.5%. During the experiment, the measured stress and deformation values are instantly fed into a controller, which can adjust the stress and deformation parameters to keep the test stable. The coupled shear flow test is carried out on a jointed sample placed in the middle of a sealed shear box. The maximum computable shear strain along the shear flow direction is 15 mm and the maximum measurable seepage pressure is 1.5 MPa. During the test, water is pumped from a tank into the joint through a water inlet under a set pressure; the outflowing water is collected and measured. A sensor is attached to the water-collecting device to timely record the amount of released water.
Model-based design of tube pumps with ultra-low flow rate pulsation
Published in SICE Journal of Control, Measurement, and System Integration, 2022
Jinhui Yang, Kentaro Hirata, Yukinori Nakamura, Kunihisa Okano, Kenichi Katoh
Currently, we are working on the design, implementation and experimental verification of a new type tube pump realizing the concept obtained from the investigation here. As mentioned earlier, due to the complexity of the mechanical structure and control, the experimental result of the 2 DoF attempt in [15] is not fully satisfactory and still reveals a flow rate pulsation about of the steady state value at best. Our tentative goal is to make it within . Since an accurate angular velocity setting is crucial in the development, a precision servo control and the rejection of the periodic disturbance via, for example, repetitive control is indispensable.