In this study, an ultra-high-precision pneumatic force servo system (UPFSS) is proposed. On the one hand, a novel air-floating pneumatic cylinder (AFPC) with an air-floating piston capable of ...independent air supply and exhaust is developed for this system, and its special flow channel design allows the air-floating piston to be suspended in the cylinder without being constrained by the pressure in the chambers. The friction force of the AFPC is less than 0.0049 N. On the other hand, a leakage chamber is constructed to simulate the clearance between the air-floating piston and the cylinder wall, and a fuzzy proportional integral (FPI)-based pressure control system (PCS) is designed for the simulated leakage chamber. Furthermore, a novel particle swarm optimization algorithm integrating Gaussian mutation and fuzzy theory (IGF-PSO) is presented. After testing, the IGF-PSO algorithm is found to have outstanding optimization performance. Then, the parameters of the FPI controller are optimized through the IGFPSO algorithm. Experimental comparisons reveal that the steady-state error achieved by the parameter-optimized pressure controller in response to the leakage condition is about 38 % smaller than that achieved by the pressure controller with parameters obtained using the trial-and-error method. Finally, the UPFSS is tested by using the optimized PCS to supply compressed air to the chamber of the AFPC. The results show that the UPFSS achieves a steady-state error of no more than 0.0279 N in the continuous step response within the range of 240 N.
•A novel high-performance PSO with Gaussian mutation and fuzzy theory is proposed.•A novel air-floating cylinder with friction force of less than 0.0049 N is developed.•An ultra-high-precision pneumatic force servo system is obtained through optimization.
Due to the time-varying characteristics of pneumatic cylinder friction force, it is usually impossible to obtain the friction force situation of ordinary pneumatic cylinders precisely. Therefore, the ...ordinary pneumatic cylinder is unable to achieve high precision servo control of the output force. In this paper, based on the principle of hydrostatic gas lubrication, a novel double-acting air-floating frictionless pneumatic cylinder is designed, which has an air-floating piston with independent air supply and exhaust channels. In the design of the air-floating frictionless pneumatic cylinder, the load capacity and air consumption of the air-floating piston are the two main points to be concerned. To this end, the effects of key parameters such as pressure relief groove position, orifice position, orifice diameter, pressure-equalizing groove size and average air film thickness on the load capacity and air consumption of the air-floating piston are analyzed by simulation. After comprehensive consideration, the key structural parameters of the air-floating piston are determined, and the prototype of the air-floating pneumatic cylinder is machining. The friction force of the prototype is tested and found to be less than 0.0098 N. In addition, the tracking experiments of continuous step and multi-frequency sinusoidal signals are conducted on the pneumatic output force control system based on the prototype, and the results show that the developed air-floating pneumatic cylinder can achieve very high precision of output force tracking control.
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•A novel double-acting air-floating frictionless pneumatic cylinder is designed.•The friction force of the developed cylinder prototype does not exceed 0.0098 N.•The prototype achieves high-precision tracking control of continuous step and multi-frequency sinusoidal output force signals.
In this article, a finite-time trajectory tracking control problem is studied for a rodless pneumatic cylinder system with disturbance in an inner outer loop framework. In the inner loop system, the ...generalized nonlinear extended state observer and the inner loop controller are designed to estimate and compensate the matched disturbances, respectively. The generalized nonlinear extended state observer designed in this article achieves desired convergence performance under relaxed existence conditions. In the outer-loop system, a super twisting extended state observer and an outer loop controller are designed to estimate and compensate the unmatched disturbances, respectively. The super twisting extended state observer is designed to realize finite-time stable by using the super twisting technology. Finally, experiment results are shown that finite-time control performances are obtained by the proposed control strategy.
To make the motion tracking control of the homemade pneumatic cylinder as accurate as possible, it is necessary to properly match the seal groove and seal ring on the piston to generate the ...appropriate friction. However, since the relationship between friction and motion control accuracy is not yet clear, and the friction affected by many factors cannot be accurately modeled, it is impossible to design the optimal seal groove with the highest possible motion control accuracy for pneumatic cylinder through theoretical calculation or simulation optimization. For this reason, an experimental optimization method is considered to select the optimal one from the six empirically designed seal grooves through a particle swarm optimization (PSO) algorithm. To cope with the shortcomings of slow convergence rate and the tendency to fall into local optimum of the basic PSO algorithm (BPSO), three improved PSO algorithms (HGMPSO-0, HGMPSO and HGMPSO-SSR) are successively proposed in this study. The first two improved algorithms are compared with other PSO variants on 23 benchmark functions tested, and the results show that HGMPSO has better overall performance. To significantly improve the search space search efficiency and make the algorithm converge faster, the search space contraction mechanism is introduced into the HGMPSO algorithm to form the HGMPSO-SSR algorithm. The experimental results show that the HGMPSO-SSR algorithm significantly outperforms other PSO variants used for comparison and successfully achieves intelligent selection of piston seal grooves for the designed homemade pneumatic cylinder.
•An intelligent selection method for the cylinder piston seal groove is proposed.•The novel improved position updating formula for PSO improves the efficiency.•The proposed method successfully achieves the optimal selection of seal grooves.
This paper presents an active disturbance rejection position control scheme for a magnetic rodless cylinder in servo systems without pressure states. It is very hard to achieve precise position ...control of magnetic rodless cylinders due to nonlinearity from large friction force and hysteresis. In this paper, the overshoot, which has a negative influence on position control, is effectively reduced by using a tracking differentiator. Furthermore, the nonlinearity is estimated by a designed extended-state observer. In addition, the self-stable region theory is used to prove the convergence of the extended-state observer. Finally, both control precision and response speed are guaranteed via a nonlinear error feedback controller in the pneumatic system. Experimental results show that the steady-state error within 0.05 mm is achieved for a step signal.
This research work has mainly concentrated on the difficulty of the movement of 3 axes on a modern trailer and hence a suitable arrangement has been designed such that the materials can be unloaded ...from the trailer in three axes without application of any impact force. Our survey is in the regard of several automobile industries that revealed some facts which are most likely difficult methods that were adopted in weighing load especially in difficulties of unloading the materials from the trailer. It is difficult to unload the materials in small, compact streets and roads; therefore, in our project these issues are rectified to unload the trailer in all three sides with ease. The control valve of the trailer is activated manually and hence the compressed air passes to the pneumatic cylinder through the valve. The ram of the pneumatic cylinder acts as a lifting arm of the trailer cabin. This project also focuses on application of self-load weighing such that the material loading and unloading weight display is viewed to cross check while unloading. The automobile engine drive is coupled to the compressor engine, so that it stores the compressed air when the vehicle is running. This compressed air is used to activate the pneumatic cylinder when the valve is activated. Also, rotation of the trailer is done with the help of gear drive system operated by the motor. The whole mechanism is controlled by the operator or driver which is near the driving seat that helps them to operate safely and easily.
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