Dynamic impact of hydraulic systems using pressure feedback for active damping

2021 ◽  
Vol 89 ◽  
pp. 454-469
Author(s):  
Min Cheng ◽  
Shaqi Luo ◽  
Ruqi Ding ◽  
Bing Xu ◽  
Junhui Zhang
Keyword(s):  
Active Damping ◽  
Hydraulic Systems ◽  
Dynamic Impact ◽  
Pressure Feedback

The Use of Derivative Pressure Feedback in High Performance Hydraulic Servomechanisms

1962 ◽  
Vol 84 (1) ◽  
pp. 8-14 ◽  
Author(s):  
T. R. Welch
Keyword(s):  
Resonant Frequency ◽  
Power Efficiency ◽  
High Performance ◽  
Corner Frequency ◽  
Hydraulic Systems ◽  
Feedback Systems ◽  
Servo Valve ◽  
Fluid Resonance ◽  
Positive Displacement ◽  
Pressure Feedback

Hydraulic servomechanisms are sometimes used to drive a load member which is predominantly inertia. The usual overriding requirements for output disturbance discrimination and high power efficiency dictate a simple closed center, flow type, servo valve, and a positive displacement actuator. The resulting transfer function relating output velocity to servo valve input current invariably includes an underdamped quadratic lag due to fluid compliance. In simple hydraulic servo systems, the corner frequency of this quadratic lag represents the absolute limit to system bandwidth. Pressure feedback systems have been devised to damp the fluid resonance so effectively that bandwidth extension beyond the quadratic corner frequency is entirely feasible. Unfortunately, such a scheme destroys the natural output disturbance discrimination inherent in the closed center hydraulic systems. A hybrid method of compensation is proposed whereby pressure feedback occurs only in the region of the resonant frequency, effectively preserving the natural output disturbance discrimination characteristics at the lower frequencies. The pressure drop across positive displacement type hydraulic actuators is a good measure of acceleration. Therefore, the technique involves feeding back this load differential pressure, sensed by electromechanical transducers, through a simple RC high pass (derivative) filter. The effectiveness of the damping is determined by the filter time constant and loop gain. Experimental results verify linear predictions of the possibility of extending the closed loop bandwidth beyond the uncompensated resonant frequency.

Guidelines for Properly Adjusting Pressure Feedback in Systems With Over-Centre Valves

2016 ◽  
Author(s):  
Henrik C. Pedersen ◽  
Torben O. Andersen ◽  
Michael R. Hansen
Keyword(s):  
Hydraulic Systems ◽  
Proportional Valve ◽  
Safety Measures ◽  
Electronic Pressure ◽  
Alternative Approach ◽  
Pressure Feedback ◽  
Energy Consuming ◽  
Standard Pressure ◽  
Linearized Model ◽  
Filter Frequency

Many mobile hydraulic systems are fitted with over centre valves for safety measures. However, it is well known that over centre valves in combination with pressure compensated flow control valves may lead to oscillatory and even unstable system behaviour. The traditional solution to overcome this problem is to use an over centre valve with a sufficiently low pilot ratio and/or include various damping orifices in the system. Both of these solutions are energy consuming and may decrease the control performance. An alternative approach is to use (electronic) pressure feedback — also referred to as active damping — to stabilise the system and damp pressure pulsations. This is not a new method, but the effect and adjustment of the filters is often misunderstood leading to incorrectly adjusted filters and degraded system performance. The focus of the current paper is therefore to explain and derive a set of guidelines for how to properly adjust a standard pressure feedback in system with an over centre valve when also considering model uncertainties, un-modelled dynamics and parameter variations. The paper takes its basis in a standard cylinder drive with an inertia load, over centre valve and a pressure compensated proportional valve. Based on a linearized model of the system, the system is analysed and it is shown that there is an optimal range for both the filter frequency and gain, which are closely linked. It is furthermore shown that these both closely affect the obtainable damping and dynamic response of the system. From the analysis a set of guidelines are derived for how to properly adjust the filter coefficients and the effect of different filter adjustments are shown and commented for the example system.

Application Analysis of Dynamic Pressure Damper in Hydraulic Systems

2015 ◽  
Vol 724 ◽  
pp. 287-294
Author(s):  
Xu Yao Mao ◽  
Yun Fei Peng ◽  
Chao Wu ◽  
Jun Hua Hu ◽  
Hong Yuan Ding
Keyword(s):  
Hydraulic System ◽  
Dynamic Pressure ◽  
System Stability ◽  
Hydraulic Systems ◽  
System Parameters ◽  
Application Analysis ◽  
Pressure Feedback ◽  
Pressure Impact ◽  
Hydraulic Cylinders

Typical hydraulic systems with inertia executive components like hydraulic cylinders are generally low in damping and lack of stability. Adding DPD to systems is an easy and effectual method to solve these problems. The performance of a mechanical dynamic pressure feedback DPD applied in a common hydraulic system was simulated while the influences of the structure and system parameters on DPD and the system were analyzed. Further research on characteristic optimization was carried out by adding accumulators to DPD. It shows that the DPD can practically improve the system stability and contain the pressure impact. The accumulators should be set appropriately before the damping orifices and have a certain ability to absorb pressure impact.

Active Ride Control for Construction Machines Based on Pressure Feedback

2019 ◽  
Author(s):  
Riccardo Madau ◽  
Andrea Vacca
Keyword(s):  
Road Construction ◽  
Hydraulic Systems ◽  
Reference Case ◽  
Machine Vibration ◽  
Main Challenge ◽  
Ride Control ◽  
Pressure Feedback ◽  
Bandwidth Limitation ◽  
Hydraulic Accumulator ◽  
High Pass

Abstract Typically, off-road construction machines are not equipped with suspensions at the wheel axles. This has led to alternative concepts that uses the working implement to mitigate the vibration transmitted to the cabin. The most common solutions are based on passive ride control (PRC) methods. A PRC usually requires a hydraulic accumulator and dissipating valves properly connected to the working hydraulics. In this way, the PRC is able to dissipate the fluid energy and damp the oscillations of the pressure inside the hydraulic actuators, with clear benefits on the machine vibration. This paper focuses instead on an active ride control (ARC) methodology, which controls the working hydraulic motion to counter-reach the machine vibrations, avoiding the use of an accumulator. The paper addresses the main challenge of designing the controller for the ARC for the reference case of a wheel loader. A high pass pressure filter control with pressure feedback is proposed for this application. The controller is first studied in a simulation model and then validated through experiments on a stock machine. The bandwidth limitation of the standard hydraulic system does not permit to achieve the same performance of a state-of-art PRC system considered as baseline. Notwithstanding, the experimental results on the proposed ARC shows significant improvements with respect to a case where no controller is used. Moreover, the proposed method could be applied with more effectiveness in hydraulic systems with higher dynamic response.

Energy-saving control for electro-hydraulic systems under time-varying negative loads

2018 ◽  
Vol 232 (5) ◽  
pp. 608-621 ◽  
Author(s):  
Mengren Jin ◽  
Qingfeng Wang
Keyword(s):  
Energy Consumption ◽  
Flow Rate ◽  
Hydraulic System ◽  
Feedback Linearization ◽  
High Gain ◽  
Inlet Pressure ◽  
Time Varying ◽  
Hydraulic Systems ◽  
Pressure Feedback ◽  
Energy Saving Control

In a hydraulic system, employment of counterbalance valve introduces sizable energy consumption. In addition, a pressure-feedback control architecture with inflexible parameters causes instability under time-varying negative loads. As an alternative, an adjustable meter-out orifice was adopted, and a stable controller was proposed in this study. By combining inlet pressure and velocity, the concept of a flow rate follower was developed. Mathematical analysis of dynamic model illustrated that both the inlet pressure and velocity converged to a range related to the flow rate follower bounds. Feedback linearization with robust control was utilized such that flow rate follower converged in the presence of parametric uncertainties; meanwhile, a high-gain load observer was constructed for disturbance compensation. The effectiveness of the controller was verified by experiments and its performance discussed. As a result, the inlet pressure was held near a specified low value, thus significantly reducing energy consumption. Also, the velocity matched the supply flow rate, and the oscillations were acceptable in applications.

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