Design of Hydraulic Force Control Systems with State Estimate Feedback

Conrad, Finn; Jensen, C. J.

doi:10.1016/s1474-6670(17)55388-4

Cited by 37 publications

(19 citation statements)

References 2 publications

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“…0'1367(_S_2_ + 2.376s + 1)(~+ I) G(,)~9.5'" 11' ' ' ' r (8) Sl-S-+l _s_+1 132. 6 42.38 (7) For disturbance rejection at plant output, the sensitive reduction problem has to be solved. Therefore, an upper tolerance is imposed on the sensitive function.…”

Section: L+g(s)p(s)mentioning

confidence: 99%

“…The method, however, relies heavily on on-line parameter estimation and consequently demands a large computational time. Conrad and Jensen [7] used combinations of velocity feed-forward, output feedback, and a Luenberger observer with state estimate feedback for force control of a double-rod hydraulic actuator. However, load variations were not considered in their study.…”

Section: Introductionmentioning

confidence: 99%

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Robust force control of a hybrid actuator using quantitative feedback theory

2007

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The use of hydraulic systems in industrial applicationshas become widespread due to their advantages in efficiency. In recent years, hybrid actuation systems, which combine electric and hydraulic technology into a compact unit, have been adapted to a wide variety of force, speed and torque requirements. A hybrid actuation system resolves energy consumption and noise problems characteristic of conventional hydraulic systems. A new, low-cost hybrid actuator using a DC motor is considered to be a novel linear actuator with various applications such as robotics, automation, plastic injection-molding, and metal forming technology. However, this efficiency gain is often accompanied by a degradation of system stability and control problems. In this paper, to satisfy robust performance requirements, tracking performance specifications, and disturbance attenuation requirements, the design of a robust force controller for a new hybrid actuator using Quantitative Feedback Theory (QFT) is presented. A family of plant models is obtained from measuring frequency responses of the system in the presence of significant uncertainty. Experimental results show that the hybrid actuator can achieve highly robust force tracking even when environmental stiffness set-point force varies. In addition, it is understood that the new system reduces energy use, even though its response is similar to that of a valve-controlledsystem.

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Section: L+g(s)p(s)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Robust force control of a hybrid actuator using quantitative feedback theory

2007

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“…Due to the near incompressibility of hydraulic oil and the coupling between the pressures of the actuator and its velocity, even minor velocity disturbances may correspond to significant disturbances in the pressures of the actuator and thus in the controlled output (Esfandiari and Sepehri, 2014). A common method of improving the performance in situations where velocity disturbances are measurable involves feed forwarding from the disturbance, see for example (Conrad and Jensen, 1987) and (Jiao et al, 2004). As will be seen in Sections 4 and 5 however, a large abrupt peaking of the control error may occur under certain operation conditions that is not reduced by feed forwarding from the velocity disturbance and appears to be a previously unaddressed phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Iterative Learning Applied to Hydraulic Pressure Control

Gøytil¹,

Hansen²,

Hovland³

2018

MIC

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This paper addresses a performance limiting phenomenon that may occur in the pressure control of hydraulic actuators subjected to external velocity disturbances. It is demonstrated that under certain conditions a severe peaking of the control error may be observed that significantly degrades the performance of the system due to the presence of nonlinearities. The phenomenon is investigated numerically and experimentally using a system that requires pressure control of two hydraulic cylinders. It is demonstrated that the common solution of feed forwarding the velocity disturbance is not effective in reducing the peaking that occurs as a result of this phenomenon. To improve the system performance, a combination of feedback and iterative learning control (ILC) is proposed and evaluated. The operating conditions require that ILC be applied in combination with a feedback controller, however the experimental system inherently suffers from limit cycle oscillations under feedback due to the presence of valve hysteresis. For this reason the ILC is applied in combination with a feedback controller designed to eliminate limit cycle oscillations based on describing function analysis. Experimental results demonstrate the efficacy of the solution where the feedback controller successfully eliminates limit cycle oscillations and the ILC greatly reduces the peaking of the control error with reductions in the RMS and peak-to-peak amplitude of the error by factors of more than 30 and 19, respectively. Stability of the proposed solution is demonstrated analytically in the frequency domain and verified on the experimental system for long periods of continuous operation.

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“…The load motion compensation was initially discussed for hydraulic actuators in [8], where it is shown that closed-loop control with force feedback is ineffective without velocity feedforward, or full state feedback. The influence of the load motion is shown for a hydraulic actuator in [9].…”

Section: Introductionmentioning

confidence: 99%

On the role of load motion compensation in high-performance force control

Boaventura

Focchi

Frigerio

et al. 2012

2012 IEEE/RSJ International Conference on Intelligent Robots and Systems

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Robots are frequently modeled as rigid body systems, having torques as input to their dynamics. A highperformance low-level torque source allows us to control the robot/environment interaction and to straightforwardly take advantage of many model-based control techniques. In this paper, we define a general 1-DOF framework, using basic physical principles, to show that there exists an intrinsic velocity feedback in the generalized force dynamics, independently of the actuation technology. We illustrate this phenomena using three different systems: a generic spring-mass system, a hydraulic actuator, and an electric motor. This analogy helps to clarify important common aspects regarding torque/force control that can be useful when designing and controlling a robot. We demonstrate, using simulations and experimental data, that it is possible to compensate for the load motion influence and to increase the torque tracking capabilities.

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Design of Hydraulic Force Control Systems with State Estimate Feedback

Cited by 37 publications

References 2 publications

Robust force control of a hybrid actuator using quantitative feedback theory

Robust force control of a hybrid actuator using quantitative feedback theory

Iterative Learning Applied to Hydraulic Pressure Control

On the role of load motion compensation in high-performance force control

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