Friction Compensation Control Research Articles

Friction compensation control method for a typical excavator system based on the accurate friction model

Traditional identification methods make it difficult to accurately determine the parameters of the friction model. Based on the LuGre friction model, a hybrid optimization algorithm (HO) is presented to address such aspects. This algorithm combines the genetic algorithm (GA) and particle swarm optimization algorithm (PSO) to obtain the globally optimal solutions. It incorporates three main improvements: introducing selection and crossover operations into the PSO algorithm, utilizing a variable inertia weight coefficient, and applying variable learning coefficients for enhanced performance. Compared to the static optimal solutions of the GA and PSO algorithms, the HO algorithm can improve the optimal solution by 40.68 % and 35.89 % respectively. The HO algorithm can achieve the highest model accuracy: the maximum identified friction error with the HO algorithm is only 1.70 kN, compared to 3.69 kN with the GA method and 8.52 kN with the PSO algorithm. Furthermore, a novel adaptive friction compensation controller (AC) is introduced based on the identification results to improve the stability and accuracy of the electro-hydraulic proportional systems of a 23-ton robotic excavator. Comparisons with existing proportional integral differential (PID) and feedforward compensation controllers (FC) highlight the superiority of the proposed adaptive controller in terms of trajectory accuracy and robustness. In sinusoidal trajectory tracking experiments, the AC method can achieve the highest tracking performance among the three controllers, and the maximum tracking error is only 11.56 mm. Compared to the FC controller, the control accuracy with the AC controller can be improved by 43.38 %. Experiments and simulations have shown that the friction compensation controller can effectively mitigate friction and other disturbances. As a result, the phenomena of crawling and flat peak phenomena can be eliminated.

Research on Pump-Controlled AGC Micro-Displacement Position Control of Lithium Battery Pole Strip Mill Based on Friction Compensation Control Strategy of Imoroved LuGre Pattern

Accurate mathematical patterning of friction has always been a significant research project in the domains of machinery and control, and has played a crucial role in the analysis, control and compensation of mechanical systems containing friction. For high-property electrohydraulic servo control systems, friction compensation is an urgent problem to be solved. The LuGre friction pattern can represent most frictional behaviors, but the LuGre friction pattern is piecewise-continuous, making it non-differentiable. Therefore, the question of how to combine the LuGre friction pattern, enhancing its tracking capacity and robust performance problem, to friction perturbation in hydraulic backstep devices is an important focus for research. In this study, the conventional LuGre friction pattern was enhanced using the continuous differentiability of a friction of rest pattern that laid the foundation of a smooth tangent function. Laying the foundation of an electrohydraulic servo pump-controlled hydraulic roll-gap thickness automatic control system (pump-controlled AGC) pattern, a self-adapting friction compensation controller laid the foundation of the enhanced LuGre pattern. The gradual tracking capacity was determined academically using conditions of parameter, uncertainty and nonlinear friction, and the position control precision of the pump-controlled AGC system was enhanced. The steady-state error of the self-adapting friction compensation control system, which laid the foundation of the enhanced LuGre pattern, attained ±0.1 μm, and the tracking capacity was better than the LuGre pattern control and the conventional PID control strategy at low input speed.

Research on Bowden Cable–Fabric Force Transfer System Based on Force/Displacement Compensation and Impedance Control

Bowden cable–fabric is a key force transfer device for flexible exoskeletons, and its precise control of force/displacement is a significant factor in the human–machine interaction of flexible exoskeletons. In this paper, a force/displacement control method based on friction compensation and impedance control was proposed based on a flexible Bowden cable–fabric force transfer testbed system. First, a set of in vitro experimental platforms simulating Bowden cable–fabric force transfer was built according to a typical flexible exoskeleton force transfer system, and following the walking gait of lower limbs, the expected force and knee joint motion were set. Secondly, the Bowden cable–fabric force transfer friction model was constructed as the basis of the system’s force transfer compensation. In addition, the stiffness model of Bowden cable–fabric and the lower leg movement model were established and combined with impedance control to realize the precise control of system displacement. Finally, the damping and stiffness parameters suitable for the system were obtained through the impedance control simulation. In terms of the experiment, an in vitro Bowden cable–fabric force transfer experimental platform was built, and the expected force with the input peak value of 40 N, 50 N, and 60 N was set. Through the friction and position compensation model of Bowden cable–fabric force transfer and impedance control, the relative root-mean-square errors of the output force and expected force were obtained as 2.53%, 2.16%, and 2.07%, respectively. Therefore, the effectiveness of the proposed method is verified, which provides a foundation for the engineering application of flexible exoskeletons.

Control of a worm-wheel gear driven rescue robot with friction compensation and its experimental verification

This paper presents the control of a rescue robot driven by the worm-wheel gear transmission. In the modeling process, the load-dependent friction of the worm-wheel gear is considered, and the governing equations for static and dynamic analyses are formulated. Especially we examine the dependency of break-in joint torques on the loading torque and directionality of motion. The friction parameters of the worm-wheel gear of a physical rescue robot are identified through experimental investigation. A friction compensation controller is then designed based on the modeling results and experimental operating conditions. And the designed controller is applied to a dual-arm rescue robot to validate its effectiveness.

Pump-Controlled AGC Micro-Displacement Position Control of Lithium Battery Pole Strip Mill Based on Friction Model

Electrode roll-forming refers to rolling a battery electrode into a preset thickness through the electro-hydraulic servo pump-controlled hydraulic roll gap thickness automatic control system (known to as pump-controlled AGC). Compared with the motor servo system, the friction problem of the electro-hydraulic servo system is more serious and the friction problem of the actuator itself is very prominent. Moreover, low-speed performance is one of its core indicators, the friction phenomenon is the most abundant during the low-speed stage and the impact on the servo system is also the most obvious. Therefore, for high-performance electro-hydraulic servo control, friction compensation is not only unavoidable, but also a very difficult problem. Aiming to influence the friction on the position control of the pump-controlled system of a lithium battery pole strip mill, the rolling mechanism and process procedure under micro-displacement position control based on the friction model were studied and compared from the perspective of considering friction factors, and a friction compensation controller based on the LuGre model was designed. The control precision of a pump-controlled AGC system was improved through combination with an adaptive robust controller. Because of the diversity of unmeasurable states of the system, a dual observer was designed, and the known model of the system was added to the observer. In the final comparative experiment, the steady-state accuracy of the friction adaptive robust compensation controller system based on the LuGre model reached ±0.3 μm, which is superior to the fuzzy IMC compensation and traditional PID control strategies.

Adaptive friction compensation control of robotic pneumatic end-effector based on LuGre model

PurposeConsidering the response lag and viscous slip oscillation of the system caused by cylinder piston friction during automatic polishing of aero-engine blades by a robotic pneumatic end-effector, the purpose of this study is to propose a constant force control method with adaptive friction compensation.Design/methodology/approachFirst, the mathematical model of the pneumatic end-effector is established based on the continuous LuGre model, and the static parameters of the LuGre model are identified to verify the necessity of friction compensation. Second, aiming at the problems of difficult identification of dynamic parameters and unmeasurable internal states in the LuGre model, the parameter adaptive law and friction state observer are designed to estimate these parameters online. Finally, an adaptive friction compensation backstepping controller is designed to improve the response speed and polishing force control accuracy of the system.FindingsSimulation and experimental results show that, compared with proportion integration differentiation, extended state observer-based active disturbance rejection controller and integral sliding mode controller, the proposed method can quickly and effectively suppress the polishing force fluctuation caused by nonlinear friction and significantly improve the blade quality.Originality/valueThe pneumatic force control method combining backstepping control with the friction adaptive compensation based on LuGre friction model is studied, which effectively suppresses the fluctuation of normal polishing force.

Tracking Control of Robot Manipulator with Friction Compensation Using Time-Delay Control and an Adaptive Fuzzy Logic System

This paper aims to highlight the critical role of robot manipulators in industrial applications and elucidate the challenges associated with achieving high-precision control. In particular, the detrimental effects of nonlinear friction on manipulators are discussed. To overcome this challenge, a novel friction compensation controller (FCC) that combines time-delay estimation (TDE) and an adaptive fuzzy logic system (AFLS) is proposed in this paper. The friction compensation controller is designed to take advantage of the time-delay estimation algorithm’s strengths in eliminating and estimating unknown dynamic functions of the system using information from the previous sampling period. Simultaneously, the adaptive fuzzy logic system compensates for the hard nonlinearities in the system and suppresses the errors generated by time-delay estimation, thus improving the accuracy of the robotic arm’s tracking. The numerical experimental results demonstrate that the proposed friction compensation controller can significantly enhance the tracking accuracy of the robotic arm, with the addition of the adaptive fuzzy logic system improving time delay estimation’s performance by an average of 90.59%. Moreover, the proposed controller is more straightforward to implement than existing methods and performs exceptionally well in practical applications.

Adaptive Terminal Sliding Mode Control of Picking Manipulator Based on Uncertainty Estimation

In this paper, a robust nonsingular fast terminal sliding mode control scheme for the picking manipulator under the condition of load change and nonlinear friction disturbance is presented. Firstly, the dynamic equation of the picking manipulator under the condition of load change and nonlinear friction disturbance is established. Then, in order to avoid the singularity problem existing in the terminal sliding mode and improve the convergence time, a new nonsingular fast terminal sliding mode control strategy is adopted to design the control law of the picking manipulator, which can guarantee the finite time convergence. The adaptive law is used to estimate the uncertainties of the system, and the finite time convergence of the system state is proved by the Lyapunov criterion. In addition, the genetic algorithm is used to identify the friction parameters to realize the nonlinear friction compensation control of the system. Finally, the simulation results of the picking manipulator under different load conditions show that the controller designed in this paper realizes the fast and accurate positioning of the picking manipulator under load change and nonlinear friction, and the control strategy is reasonable and effective.

Modeling, Identification, and Compensation Control of Friction for a Novel Dual-Drive Hydrostatic Lead Screw Micro-Feed System

This paper investigates the transmission performance of a novel dual-drive hydrostatic lead screw micro-nano feed system (DDHLS) that can obtain extremely low speed. Firstly, the oil film liquid friction of hydrostatic transmission is modelled, and the calculation model of oil film dynamic friction is proposed based on the variable viscosity theory. Secondly, on this basis, combined with the LuGre friction model, a novel all-components refinement friction identification method (ACRFIM) for DDHLS was developed. The friction parameters of the feed drive components such as LM guide and hydrostatic lead screw can be identified independently using the proposed method, ensuring precise friction force modelling in all components. Then, an all-component adaptive friction compensation control algorithm (AACA) was designed by introducing the temperature and disturbance influence factors into the friction model and considering the influence of the dynamic friction of liquid. The experiments illustrate that the calculation accuracy of the oil film friction model based on the variable viscosity theory is substantially improved. DDHLS can effectively suppress the adverse effects of nonlinear friction, and the proposed AACA has an obvious compensation effect for the friction of the time-varying system.

Automatic Control of Food Machinery Based on Neural Network and Computational Torque Compounding

In order to improve the effect of automatic control of food machinery, this paper combines neural network and computational torque compounding to study the automatic control system of food machinery to improve the effect of automatic control of food machinery. Moreover, this paper studies the problem of strong time-varying nonlinear friction disturbance in the servo motion system, and analyzes the friction nonlinearity at low speed and commutation motion of the system. In addition, this paper introduces the application requirements for the nonlinear friction compensation control method, and proves that the designed controller can maintain the stability of the system under the condition of strong nonlinear time-varying friction through the Lyapunov stability principle. The experimental study shows that the control strategy given in this paper can not only effectively improve the tracking speed of the joints, but also effectively alleviate the later tremor, and the automatic control effect of food machinery based on neural network and computational torque compounding has certain effects.

Adaptive force tracking control of electrohydraulic systems with low load using the modified LuGre friction model

The force tracking performance of controllers is seriously degraded by the complex friction behaviors when the electrohydraulic system applies low load. The existing LuGre model is employed in the motion control system with the known trajectory. In this work, a modified LuGre model combined with a zero-velocity crossing window is established to address the lag issue and model oscillation in force control system. Then, the Stribeck curve in the friction model is accurately obtained using a fast measurement method, and the impact of friction parameters on the accuracy of the LuGre model is analyzed. Next, an adaptive friction compensation control scheme is proposed for the electrohydraulic system with low load using the modified LuGre model to compensate for dynamic friction behavior and improve the force tracking performance. The uncertain friction parameters are tuned online to reduce the force error of the low-velocity region via the derived adaptive law and a dual-observer. The disturbance observer is effectively integrated to reduce the negative influence of unconsidered dynamics. Finally, comparative experiments are conducted to verify the effectiveness of the proposed controller in static and dynamic loading modes.

Adaptive Friction Compensation for a Novel Two-Axis Differential Microfeed System

The conventional drive feed system inevitably enters the nonlinear creep region at very low speed. This seriously affects its low-speed performance and tracking accuracy. The new two-axis differential microfeed system (TDMS) can overcome the low-speed crawling and creep phenomenon caused by the inherent characteristics of the traditional electromechanical servo system structure. In this study, the dynamic model of TDMS is first established, and the LuGre friction model is improved according to its motion characteristics. The friction model of the screw nut whole assembly of TDMS is established. On this basis, two nonlinear observers are designed to estimate the internal state of the friction model, and the TDMS adaptive friction compensation controller is designed to estimate the uncertain parameters in TDMS through the parameter adaptive law. The global asymptotic stability of the TDMS controller is proved by Lyapunov theorem. Finally, the experimental verification is carried out by using dSPACE system. The results showed that the proposed TDMS adaptive friction compensation controller has good control accuracy. And it can effectively compensate the friction torque of lead screw nut differential drive. Compared with the application of traditional PID controller in TDMS, the tracking accuracy is improved by an order of magnitude.

A novel steering-by-wire system with road sense adaptive friction compensation

This paper proposes an adaptive friction torque compensation scheme for the vehicle steer-by-wire (SBW) system. Firstly, the overall system structure is analyzed into a steering wheel subsystem and an active steering subsystem. Specifically, the road sense torque of the SBW system is represented by a plant model from the road sense motor input current to the steering wheel torque. Next, a road torque expression related to vehicle speed and road conditions is designed for the steering wheel subsystem. Furthermore, the torque expression has been corrected using damping model and coulomb friction model. Then, an adaptive friction compensation controller is designed for the SBW system, which adopts a LuGre dual observer and backstepping method (BS) to improve tracking accuracy by dealing with complex friction parameters estimation problems, and use an adaptive sliding mode control (SMC) component to deal with external disturbance and chattering. The stability and robustness of the adaptive friction compensation control system are verified through Lyapunov and frequency domain analysis. Finally, numerical simulations, hardware-in-the-loop (HIL) and vehicle experiments are carried out under various conditions. Numerical and experimental results demonstrate that the designed road sense conforms to the operating standard, and the proposed adaptive friction compensation controller has not only high compensation tracking accuracy but also high robustness. The proposed approach effectively reduces the steering wheel torque fluctuation caused by the mechanical friction, and can adaptively match different actuators.

Medical Grabbing Servo System with Friction Compensation Based on the Differential Evolution Algorithm

This paper introduces a pneumatic finger cylinder servo control system for medical grabbing. First, according to the physical structure of the proportional directional valve and the pneumatic cylinder, the state equation of the gas in the servo system was obtained. The Stribeck friction compensation model of a pneumatic finger cylinder controlled by a proportional valve was established and the experimental platform built. To allow the system output to better track the change in the input signal, the flow-gain compensation method was adopted. On this basis, a friction compensation control strategy based on a differential evolution algorithm was proposed and applied to the position control system of a pneumatic finger cylinder. Finally, the strategy was compared with the traditional proportional derivative (PD) strategy and that with friction compensation. The experimental results showed that the position accuracy of the finger cylinder position control system can be improved by using the friction compensation strategy based on the differential evolution algorithm to optimize the PD parameters.

Research on Adaptive Friction Compensation of Digital Hydraulic Cylinder Based on LuGre Friction Model

This paper aims to eliminate nonlinear friction from the performance of the digital hydraulic cylinder to enable it to have good adaptive ability. First, a mathematical model of a digital hydraulic cylinder based on the LuGre friction model was established, and then a dual-observer structure was designed to estimate the unobservable state variables in the friction model. The Lyapunov method is used to prove the global asymptotic stability of the closed-loop system using the adaptive friction compensation method. Finally, Simulink is used to simulate the system performance. The simulation results indicate that the addition of adaptive friction compensation control can effectively reduce system static error, suppress system limit loop oscillation, “position decapitation,” “speed dead zone,” and low-speed creep phenomena, and improve the overall performance of the digital hydraulic cylinder. The control method has practical application value for improving the performance index of the digital hydraulic cylinder.

Adaptive Friction Compensation Control for a Roll-Isolated Strapdown Inertial Navigation System

In order to meet the requirements of miniaturization and low cost of rolling missiles, the roll-isolated strapdown inertial navigation systems began to be applied to such weapon systems. This paper proposes an adaptive control approach based on LuGre friction torque model to eliminate the influence of the nonlinear characteristics of the friction torque of the roll-isolated platform at low speed. Two nonlinear state observers are used to estimate the unknown state variables in LuGre model, and the parameters of the model are adaptively estimated. The global asymptotic stability of the system is proved by Lyapunov method. The simulation results show that compared with the traditional control approaches, this approach improves the control precision and low-speed performance of the roll-isolated platform, and can meet the performance requirements of the roll-isolated strapdown inertial navigation system.

Observer-based interval type-2 fuzzy friction modeling and compensation control for steer-by-wire system

This paper studies the tracking control of the SbW system with unknown nonlinear friction torque and the unmeasured angular velocity. An observer-based adaptive interval type-2 fuzzy logic system controller is proposed to eliminate the adverse influence of the friction torque on the SbW system. Firstly, the angular velocity of the front wheels is estimated via the observer, such that the system sensitivity to measurement noise, the hardware cost, and the structural complexity are reduced. Then, an interval type-2 fuzzy logic system (IT2 FLS) is used to model the friction torque, in which the model and parameters are not effectively identified. IT2 FLS has a more exceptional ability to deal with uncertainties than the traditional type-1 fuzzy logic system (T1 FLS), so the friction modeling based on IT2 FLS has more satisfactory effect in practical application. Finally, an adaptive interval type-2 fuzzy logic system controller is proposed to achieve excellent tracking performance. The tracking error can be guaranteed to converge asymptotically to zero by the Lyapunov stability theory. The numerical simulations and hardware-in-loop (HIL) experiments verify the effectiveness and superiority of the proposed friction modeling method and control strategy.

Friction Compensation Control to Achieve Pre-specified Transient and Steady-state Performance

Friction Compensation Control to Achieve Pre-specified Transient and Steady-state Performance

Master cylinder pressure reduction logic for cooperative work between electro-hydraulic brake system and anti-lock braking system based on speed servo system

As one feasible solution of brake-by-wire systems, electro-hydraulic brake system has been made available into production recently. Electro-hydraulic brake system must work cooperatively with the hydraulic control unit of anti-lock braking system. Due to the mechanical configuration involving electric motor + reduction gear, the electro-hydraulic brake system could be stiffer in contrast to a conventional vacuum booster. That is to say, higher pressure peaks and pressure oscillation could occur during an active anti-lock braking system control. Actually, however, electro-hydraulic brake system and anti-lock braking system are produced by different suppliers considering brake systems already in production. Limited signals and operations of anti-lock braking system could be provided to the supplier of electro-hydraulic brake system. In this work, a master cylinder pressure reduction logic is designed based on speed servo system for active pressure modulation of electro-hydraulic brake system under the anti-lock braking system–triggered situation. The pressure reduction logic comprises of model-based friction compensation, feedforward and double closed-loop feedback control. The pressure closed-loop is designed as the outer loop, and the motor rotation speed closed-loop is drawn into the inner loop of feedback control. The effectiveness of the proposed controller is validated by vehicle experiment in typical braking situations. The results show that the controller remains stable against parameter uncertainties in extreme condition such as low temperature and mismatch of friction model. In contrast to the previous methods, the comparison results display the improved dynamic cooperative performance of electro-hydraulic brake system and anti-lock braking system and robustness.

Friction compensation control of a feed drive system operated in a vacuum

In a feed drive system, friction is a typical nonlinear component that increases the complexity of the dynamic behavior. A feed drive system equipped with rolling contact components, such as ball screws and linear motion guides, undergoes complicated friction behavior. In this regard, various techniques have been proposed to decrease the effect of friction and thus achieve the precise control of the feed drive system. Friction compensation control is a widely used technique that cancels out the friction force by applying an additional driving force that corresponds to the friction estimated by a friction model. A variety of friction models have been proposed to estimate the friction force accurately for friction compensation control. However, conventional friction models have focused on estimating the friction force of a feed drive system operating in atmospheric pressure although air pressure affects the friction characteristics. The accuracy of the conventional friction models might decrease for a feed drive system operated in a vacuum. This paper presents a friction compensation controller on the basis of a new friction model that considers the effect of the vacuum pressure on friction. A vacuum chamber that can control the vacuum pressure and a vacuum-compatible feed drive system are constructed to measure the friction force at various vacuum pressures. The relationship between the friction characteristics and the vacuum pressure is investigated on the basis of the experimental results and applied to the friction model. A friction compensation controller based on the friction model and Kalman filter is designed and evaluated experimentally.