A control algorithm for a 3-RPS parallel platform driven by pneumatic cylinders is discussed. All cylinders are controlled by proportional directional valves while the kinematic and dynamic ...properties of the system are modeled. The method of adaptive robust control is applied to the controller using a back-stepping approach and online parameter estimation. To compensate for the uncertainty and the influence caused by estimations, a fast dynamic compensator is integrated in the controller design. To prevent any influence caused by the load applied to the moving platform changing in a practical working situation, the identification of parameters is taken as the initialization of unknown parameters in the controller, which can improve the adaptability of the algorithm. Using these methods, the response rate of the parameter estimation and control performance were improved significantly.The adverse effects of load and restriction forces were eliminated by the initialization and online estimation.Experiments under different situations illustrated the effectiveness of the adaptive robust controller with parameter initialization, approaching average tracking errors of less than 1%.
The arbitrary position control of cylinder has always been the hard challenge in pneumatic system. We try to develop a cylinder position servo control method by combining fuzzy PID with the ...theoretical model of the proportional valve-controlled cylinder system. The pressure differential equation of cylinder, pressure-flow equation of proportional valve, and moment equilibrium equation of cylinder are established. And the mathematical models of the cylinder driving system are linearized. Then fuzzy PID control algorithm is designed for the cylinder position control, including the detail analysis of fuzzy variables and domain, fuzzy logic rules, and defuzzification. The stability of the proposed fuzzy PID controller is theoretically proved according to the small gain theorem. Experiments for targets position of 250 mm, 300 mm, and 350 mm were done and the results showed that the absolute error of the position control is less than 0.25 mm. And comparative experiment between fuzzy PID and classical PID verified the advantage of the proposed algorithm.
Purpose
– Intelligent pneumatic actuator (IPA) is a new generation of actuator developed for Research and Development (R&D) purposes in the academic and industrial fields. The purpose of this paper ...is to show the application of optical encoder and pressure sensor in IPA, to develop a real-time model similar to the existing devices, and to assess the position control performance using a proportional-integrative (PI) controller and a bang-bang controller in real-time.
Design/methodology/approach
– A micro optical encoder chip is used to detect cylinder rod position by reading constructed laser stripes on a guide rod, whereas a pressure sensor is used to detect the chamber pressure reading. To control the cylinder movements by manipulating pulse-width modulation (PWM) cycles, two unit valves of two ports and two positions were used. A PI controller and a bang-bang controller are used with suitable gain value to drive the valve using PWM to achieve the target actuator position.
Findings
– The results show the experimental results of the closed-loop position tracking performance of the system using a data acquisition (DAQ) card over MATLAB software.
Originality/value
– This paper presents a real-time model used to replace the microcontroller-based system from previous IPA design. The paper proposes two control strategies, PI and bang-bang, to control position using encoder and pressure reading.
Recent research has shown that robust and precise high-speed control of pneumatic actuators is practicable, by application of advanced control techniques such as model-based adaptive and sliding-mode ...control. However, the resulting need for full state-based feedback and feedforward control-in particular, the measurement of air pressures-increases both the cost and complexity of the overall system. In this paper, we consider the problem of design of observers to estimate the chamber pressure variables in a cylinder actuator. Since the cylinder pressures are not simultaneously observable because of the nature of cylinder dynamics, we first propose a continuous gain observer in which the pressure on one side of the cylinder is measured and the pressure on the other side is estimated. Next, we propose a sliding-mode observer where numerically estimated acceleration is used in order to observe both pressures, with ultimate bounded stability. A sliding-mode controller is proposed, whose sensitivity to errors under the sliding-mode observer is studied. The proposed observers are simple, effective and easy to implement. Results of experimental implementation illustrate the practical effectiveness of the new observers.
Stroke is a common condition resulting in 30 000 people per annum left with significant disability. In patients with severe arm paresis after stroke, functional recovery in the affected arm is poor. ...Inadequate intensity of treatment is cited as one factor accounting for the lack arm
recovery found in some studies. Given that physical therapy resource is limited, strategies to enhance the physiotherapists' efforts are needed. One approach is to use robotic techniques to augment movement therapy. A 3-d.o.f. pneumatic robot has been developed to apply physiotherapy to the
upper limb. The robot has been designed with a workspace encompassing the reach-retrieve range of the average male. Slight non-linearities in the response of the pneumatic system are observed and explained. Building upon previous work that used an error-prone custom force sensor, a commercial
6-d.o.f. force sensor is used to apply impedance control in 3 d.o.f. on the robot.
This paper mainly comprises of design and fabrication of torque value check by using pneumatics as a base concept. The machines which detect the play of the wheel end which is placed in the steering ...column for converting the rotational motion to angular motion of the tyres. The torque meter which displays the play of the wheel end through a digital output. Since the customers prefer their own specification there is a chance of misplacement in the batch production. The steering column manufacturing unit faces a serious crisis. In order to overcome this Japanese technique called Poka Yoke (error proof) has been infused with this design. The Programmable Logical Circuits (PLC) controlled unit which plays the vital role in the sequencing the pneumatic cylinders according to operations planned. The sensors placed in the proper orientation helps the worker to detect the error in the work piece. With this an additional printer device is installed which automatically prints the label code for the product. The sensor allows the operator to paste the label in the correct position. If the label is positioned in the wrong place the led emits red light to glow or the green light glows which indicates the part is correct.
Although the performance and reliability of pneumatic cylinders depend to a great extent on the friction generated at the seals, the friction characteristics have not been widely studied. Both the ...literature and manufacturers' catalogues rarely discuss the friction characteristics of pneumatic cylinders, and the lack of friction models limits the design, optimisation, and analysis of pneumatic cylinder systems. In seeking to improve the characteristics of pneumatic cylinders and to clarify the friction phenomenon, this paper describes friction force measurement tests carried out in pneumatic cylinders of six different diameters, from 32 to 100 mm. An experimental apparatus was designed to assess the effect of a broad range of operating conditions, where the velocity and pressure of the cylinder chambers are controlled independently. Measurements of friction force are shown for velocities of up to 0.5 m/s and pressures of up to 0.8 MPa. The data obtained will be useful for developing a suitable friction model, and the experimental apparatus will allow study of the effects on the friction force of different types of seal, lubricant, and cylinder barrel.
Stroke is a common condition resulting in 30,000 people per annum left with significant disability. In patients with severe arm paresis after stroke, functional recovery in the affected arm is poor. ...Inadequate intensity of treatment is cited as one factor accounting for the lack of arm recovery found in some studies. Given that physical therapy resource is limited, strategies to enhance the physiotherapists' efforts are needed. One approach is to use robotic techniques to augment movement therapy. A three degree-of-freedom pneumatic robot has been developed to apply physiotherapy to
the upper limb. The robot has been designed with a workspace encompassing the reach-retrieve range of the average male. Control experiments have applied force and then position only controllers to the pneumatic robot. These controllers are combined to form a
position-based impedance control strategy on all degrees of freedom of the robot. The impedance controller performance was found to be dependent upon the specified impedance parameters. Initial experiments attaching the device to human subjects have indicated great potential for the device.
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