scholarly journals Hysteresis Control in Pump-Controlled Systems—A Way to Reduce Mode-Switch Oscillations in Closed and Open Circuits

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 424
Author(s):  
Samuel Kärnell ◽  
Liselott Ericson
Keyword(s):  
Open Circuit ◽  
Switching Behavior ◽  
Mode Switching ◽  
Hydraulic Systems ◽  
Mode Switch ◽  
Pressure Sensing ◽  
Controlled Systems ◽  
Huge Impact ◽  
Prime Movers ◽  
Hysteresis Control

There is growing interest in using electric motors as prime movers in mobile hydraulic systems. This increases the interest in so-called pump-controlled systems, where each actuator has its own drive unit. Such architectures are primarily appealing in applications where energy efficiency is important and electric recuperation is relevant. An issue with pump-controlled systems is, however, mode-switch oscillations which can appear when the pressure levels in the system are close to the switching condition. In this paper, the mode-switching behavior of different generalized closed and open circuit configurations is investigated. The results show that the choice of where to sense the pressures has a huge impact on the behavior. They also show that, if the pressure sensing components are properly placed, closed and open circuits can perform very similarly, but that mode-switch oscillations still can occur in all circuits. Active hysteresis control is suggested as a solution and its effectiveness is analyzed. The outcome from the analysis shows that active hysteresis control can reduce the risk for mode-switch oscillations significantly.

Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

2009 ◽  
Author(s):  
Michael B. Rannow ◽  
Perry Y. Li
Keyword(s):  
Hydraulic System ◽  
Check Valve ◽  
Fluid Flows ◽  
Soft Switching ◽  
Total System ◽  
System Efficiency ◽  
Hydraulic Systems ◽  
Controlled Systems ◽  
Flow Through ◽  
Hydraulic Valve

A method for significantly reducing the losses associated with an on/off controlled hydraulic system is proposed. There has been a growing interest in the use of on/off valves to control hydraulic systems as a means of improving system efficiency. While on/off valves are efficient when they are fully open or fully closed, a significant amount of energy can be lost in throttling as the valve transitions between the two states. A soft switching approach is proposed as a method of eliminating the majority of these transition losses. The operating principle of soft switching is that fluid can temporarily flow through a check valve or into a small chamber while valve orifices are partially closed. The fluid can then flow out of the chamber once the valve has fully transitioned. Thus, fluid flows through the valve only when it is in its most efficient fully open state. A model of the system is derived and simulated, with results indicating that the soft switching approach can reduce transition and compressibility losses by 79%, and total system losses by 66%. Design equations are also derived. The soft switching approach has the potential to improve the efficiency of on/off controlled systems and is particularly important as switching frequencies are increased. The soft switching approach will also facilitate the use of slower on/off valves for effective on/off control; in simulation, a valve with soft switching matched the efficiency an on/off valve that was 5 times faster.

298Atrioventricular synchronous pacing in leadless ventricular pacemaker is safe and effective in patients with paroxysmal AV block and atrial arrhythmias

EP Europace ◽  
2020 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
C Garweg ◽  
S K Khelae ◽  
J Y S Chan ◽  
L Chinitz ◽  
P Ritter ◽  
...  
Keyword(s):  
Normal Sinus Rhythm ◽  
Sinus Bradycardia ◽  
Mode Switching ◽  
Ventricular Rate ◽  
Low Grade ◽  
Atrial Arrhythmias ◽  
Av Block ◽  
Mode Switch ◽  
Switching Algorithm ◽  
Normal Sinus

Abstract Funding Acknowledgements Medtronic, Inc. Background/Introduction Accelerometer (ACC)-based AV synchronous pacing by tracking atrial activity is feasible using a leadless ventricular pacemaker. Patients may experience variable AV conduction (AVC) and/or atrial arrhythmias during the lifetime of their device. ACC-based AV synchronous pacing should facilitate AVC and pace appropriately in those two common rhythms. Purpose To characterize the behavior of ACC-based AV synchronous pacing algorithms during paroxysmal AV block (AVB) and atrial arrhythmias. Methods The MARVEL2 (Micra Atrial tRacking using a Ventricular accELerometer) was a 5-hour acute study to assess the efficacy of atrial tracking with a temporarily downloaded algorithm into a Micra leadless pacemaker. Patients with a history of AVB were eligible for inclusion. The MARVEL2 algorithm included a mode-switching algorithm that switched between VDD and VVI-40 depending upon AVC status. The AVC algorithm requires 2 ventricular paces (VP) at 40 bpm out of 4 pacing cycles to switch to VDD. Results Overall, 75 patients (age 77.5 ± 11.8 years, 40% female, median time from Micra implant 9.7 months) from 12 centers worldwide were enrolled. During study procedures, 40 patients (53%) had normal sinus rhythm with complete AVB, 18 (24%) had 1:1 AVC, 5 (7%) had varying AVC status, 8 (11%) had atrial arrhythmias, and 2 other rhythms.  Two patients with complete AVB had the AVC mode switch feature disabled due to an idioventricular rate >40 bpm.  Among the 40 subjects with a predominant 3rd degree AVB and normal sinus function the median %VP was 99.9% compared to 0.2% among those with 1:1 AVC (Figure). In the patients with 1:1 AVC, there were 64 opportunities to AVC mode switch with 48 switching to VDI-40. In the other 16 cases (2 patients) the mode remained VDD due to sinus bradycardia varying between 40-45 bpm. High %VP was observed in 2 patients with 1:1 AVC and sinus bradycardia <40 bpm. The AVC mode switch minimized %VP (<1%) in patients with PR intervals > 300 ms (N = 2). Among patients with varying AVC, the algorithm appropriately switched to VDD when the ventricular rate was paced at 40 bpm. During infrequent AVB or AF with ventricular response >40 bpm, VVI-40 mode was maintained. In patients with AF, the ACC signal was of low amplitude and there was infrequent sensing, resulting in VP at the lower rate (50 bpm). In the one patient with atrial flutter, the ACC was intermittently detected, resulting in VP at 67 bpm (IQR 66-67 bpm). Conclusion(s) The mode switching algorithm in the MARVEL2 reduced %VP in patients with 1:1 AVC and appropriately switched to VDD during complete AVB.  If greater AV synchrony or rate support is required, disabling the AVC algorithm may be appropriate for low grade AVB or idioventricular rhythms. In the presence of atrial arrhythmias, the algorithm paced near the lower rate. Abstract Figure. Distribution of VP% by heart rhythm

Analysis of Vehicle Longitudinal Dynamics for Longitudinal Ride Comfort

2006 ◽  
Author(s):  
Shiang-Lung Koo ◽  
Han-Shue Tan ◽  
Masayoshi Tomizuka
Keyword(s):  
Time Domain ◽  
Ride Comfort ◽  
Vehicle Control ◽  
Switching Behavior ◽  
Mode Switching ◽  
Longitudinal Motion ◽  
Analytical Prediction ◽  
Longitudinal Model ◽  
The Time Domain ◽  
The Impact

Longitudinal ride comfort is one of the most crucial features to most advanced vehicle control systems. Literature review shows that the ride comfort analysis in vehicle longitudinal motion can be divided into two categories: time domain and frequency domain. Most vehicle longitudinal control designs incorporate jerk and acceleration constraints from the time-domain comfort criterion. However, the vehicle longitudinal characteristics in the frequency range important to passenger ride comfort are rarely discussed in the vehicle control literature. This paper proposes an improved vehicle longitudinal model that captures tire and suspension modes accurately and investigates the impact of these often-ignored vehicle resonant modes to ride comfort. This study shows that the "tire-mode switching behavior" affects longitudinal ride comfort of a stopping vehicle rather than the suspension. A passenger car was tested as an example, and the collected data verified the analytical prediction from the improved vehicle longitudinal model.

scholarly journals Investigating the Mode Switching Behavior from Different Non-Car Modes to Car: The Role of Life Course Events and Policy Opportunities

2019 ◽  
Vol 2673 (3) ◽  
pp. 676-685 ◽  
Author(s):  
Weibo Li ◽  
Maria Kamargianni
Keyword(s):  
Life Course ◽  
Mode Choice ◽  
Point Of View ◽  
Policy Implications ◽  
Switching Behavior ◽  
Mode Switching ◽  
Desirable Outcome ◽  
First Child ◽  
Binary Logit ◽  
Logit Regression Model

Life course events can lead to a habitual change of mode choice, which can sometimes be from non-car modes to the car, which is not a desirable outcome from a sustainable point of view. This research studied in depth the mode switching behavior from a range of non-car modes to the car, to identify opportunities for policy intervention to hold back such changes in habit toward car usage. Retrospective commute mode choice and various life course event data over four observation periods were collected. A mixed binary logit regression model was developed to study mode switching behavior from car to non-car modes, followed by the development of a set of “mirror models” (also mixed binary logit) that evaluated mode switches from non-car modes to the car. By observing their distinct reactions to life course events, it was found that users of different types of non-car modes display distinct mode switching behavior, especially in relation to getting married, having their first child and in response to different degrees of commute distance change. A thorough discussion on the policy implications of these findings is provided.

Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Michael B. Rannow ◽  
Perry Y. Li
Keyword(s):  
Hydraulic System ◽  
Check Valve ◽  
Fluid Flows ◽  
Soft Switching ◽  
Total System ◽  
System Efficiency ◽  
Hydraulic Systems ◽  
Controlled Systems ◽  
Flow Through ◽  
Hydraulic Valve

A method for significantly reducing the losses associated with an on/off controlled hydraulic system is proposed. There has been a growing interest in the use of on/off valves to control hydraulic systems as a means of improving system efficiency. While on/off valves are efficient when they are fully open or fully closed, a significant amount of energy can be lost in throttling as the valve transitions between the two states when the switching times are not negligible. A soft switching approach is proposed as a method of eliminating the majority of these transition losses. The operating principle of soft switching is that fluid can temporarily flow through a check valve or into a small chamber while valve orifices are partially closed. The fluid can then flow out of the chamber once the valve has fully transitioned. Thus, fluid flows through the valve only when it is in its most efficient fully open state. A model of the system is derived and simulated, with results indicating that the soft switching approach can reduce transition and compressibility losses by 81% and total system losses by 64%. The soft switching approach has the potential to improve the efficiency of on/off controlled systems and is particularly beneficial as switching frequencies are increased. The soft switching approach will also facilitate the use of slower on/off valves for effective on/off control; in simulation, a valve with soft switching matched the efficiency of an on/off valve that was 4.4 times faster.

Novel Open Circuit Displacement Control Architecture in Heavy Machinery

2014 ◽  
Author(s):  
Roman Ivantysyn ◽  
Jürgen Weber
Keyword(s):  
Large Scale ◽  
Mass Movement ◽  
Operating Cost ◽  
Open Circuit ◽  
Closed Circuit ◽  
Small Scale ◽  
Hydraulic Systems ◽  
Displacement Control ◽  
Heavy Machinery ◽  
Mobile Machinery

Motivated by the ever-stricter demands by lawmakers to lower emissions of mobile machinery and increasing fuel prices, mobile machinery has gone through a paradigm shift. Fuel efficiency has become a major selling point of machine producers. Even the heavy machinery branch, which is mainly dominated by reliability, productivity and serviceability, has started to feel this change. Hydraulic systems of large scale, as can be found in mining excavators, have typically been based on simplicity and durability. Typical architectures are open-center hydraulic systems, which were designed with robustness and productivity in mind; however they lack competiveness with other hydraulic systems in terms of energy efficiency. Displacement control has shown promising potential especially in multi-actuator machines such as excavators. The technology has so far been demonstrated in closed circuit applications on small-scale machines (below 30 t). Large scale excavators however should in general be more suitable for displacement control due to their relatively small hydraulic component cost compared to the machine and operating cost, larger energy recovery potential due to larger mass movement, more flexibility in space management and greater hydraulic power installed. Large machines feature already several smaller pumps instead of a single large pump, which is important with respect to the fact that displacement control is based on one pump per actuator. A challenge for displacement control on large-scale machinery is handling their high volumetric flow-demands on the system. Today many large excavators feature a float valve, which short-circuits the cylinder chambers and ensures rapid lowering of the attachment under aiding load. Float valves ensure fast cycle times and are essential for high productivity, however incorporating this feature in displacement control is a challenge, especially in closed circuit systems. Open circuit displacement control systems have greater flexibility than closed circuit solutions in working with float-valves and dealing with the high volumetric flows. Additionally the open circuit architecture is ideal for pump-flow-sharing, the strategy to connect two or more pumps with one actuator, which can be practiced when not all actuators move at the same time. This paper compares displacement control in open circuit form with valve-controlled actuation in a mining excavator and shows several fuel saving potentials. The Open Center system was simulated and results were validated with measurements. The proposed open circuit displacement control solutions are implemented virtually and replace the valve-controlled system. Components and system-architecture were carefully chosen in order to ensure reliability, minimal component changes and redundancy that compare to the robustness of today’s system.

Direct Driven Pump Control of Hydraulic Cylinder for Rapid Vertical Position Control of Heavy Loads: Energy Efficiency Including Effects of Damping and Load Compensation

2018 ◽  
Author(s):  
Heikki Kauranne ◽  
Teemu Koitto ◽  
Olof Calonius ◽  
Tatiana Minav ◽  
Matti Pietola
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Position Control ◽  
Open Circuit ◽  
Vertical Position ◽  
Hydraulic Systems ◽  
Heavy Load ◽  
Load Compensation ◽  
Electric Drives ◽  
Measurement Results

The ever-tightening government-enforced regulations for more energy efficient and less polluting machines and the simultaneous fast development of electric drives have caused hydraulic systems to lose ground to electric drives. One promising solution to improve the status of hydraulics in this competition are the Direct Driven Hydraulic (DDH) systems, aka electro-hydraulic actuators (EHAs), which are characterized by a closed circuit type and a servo motor driven speed-controlled pump controlling the actuator. Due to this topology, they offer a possibility of reaching higher energy efficiencies compared to traditional open circuit type valve-controlled systems and simultaneously they offer the high accuracy and dynamics of these. Typical applications where DDHs have been used are, in the area of mobile equipment, modern commercial and military aircrafts and some lift trucks, and in the area of stationary applications, mostly presses. In all of these, the actuators produce relatively slow motions. In this experimental study, a DDH system is applied to a stationary industrial vertical position control application where a very rapid movement of a heavy load is required. This brings out some unwanted fluctuation phenomena not encountered with slower motion velocities. Here we are striving for avoiding these phenomena by adding damping to the system. In addition, it is studied whether the good energy efficiency of DDH systems could be enhanced with load-compensation. The presented measurement results include the system behavior regarding the smoothness of positioning, the fluctuations of pressures, forces, and power, and finally the energy consumption with three different system configurations: basic DDH, load-compensated DDH, and load-compensated and damped DDH. The measured energy consumptions are compared against results gained in simulating a conventional valve-controlled system driving the same application. The measurement results manifest that energy consumption wise significant benefits are achievable with DDH, especially in combination with hydraulic load compensation. However, without added damping the motion involved marked vibrations in the end of the upward and downward strokes. Added damping eliminated these vibrations, but at the cost of reduced energy efficiency. Due to this, the solution for the fluctuation and vibration problem should be sought by developing a control strategy that produces a smoother but as fast motion.

Single Edge Meter Out Control for Mobile Machinery

2014 ◽  
Author(s):  
Milos Vukovic ◽  
Hubertus Murrenhoff
Keyword(s):  
Control Strategies ◽  
Industrial Applications ◽  
Mode Switching ◽  
Hydraulic Systems ◽  
Single Edge ◽  
Load Pressure ◽  
System Architectures ◽  
Operating Modes ◽  
System Pressure ◽  
Mobile Machinery

To decrease throttling losses in mobile hydraulic systems a number of new system architectures have been introduced in recent years. The concept of independent metering (IM), developed in the seventies, shows a lot of promise [1]. By allowing the meter-in as well as meter-out edges to be controlled separately, additional operating modes are created allowing a more efficient adaptation of system pressure to load pressure [2, 3]. Despite these advantages IM circuits have yet to find their way into industrial applications. This is mainly due to the related increase in component costs and more demanding control strategies. Additionally, the effect of mode switching on actuator motion and operator comfort is still unclear and considered to be a challenge. The STEAM mobile hydraulic system currently being developed in Aachen, Germany uses a number of new features to improve total machine efficiency [4]. Among others is the use of a new independent metering circuit called single edge meter-out control. Unlike other IM configurations, only one proportional valve is used to control cylinder motion. This paper introduces the new concept and discusses its advantages.

Using Leakage to Stabilize a Hydraulic Circuit for Pump Controlled Actuators

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Longke Wang ◽  
Wayne J. Book
Keyword(s):  
Energy Efficiency ◽  
System Dynamics ◽  
Numerical Simulations ◽  
Lower Cost ◽  
System Stability ◽  
Mode Switching ◽  
Hydraulic Circuit ◽  
Controlled System ◽  
Fluid Leakage ◽  
Controlled Systems

Pump controlled hydraulic actuators offer higher energy efficiency than valve controlled actuators. However, there exists mode switching in pump controlled systems and instability may arise when a single rod cylinder is implemented. This paper examines the problem of system stability in a pump controlled system with single rod cylinders. It is shown that the system dynamics have a stable tendency or an instable tendency corresponding to different cylinder movements. The paper shows system instability can be avoided by controlling fluid leakage, and two applicable methods are presented: physical leakage compensation and virtual leakage compensation, which can be applied depending on applications. Experiments and numerical simulations are presented. Results show that the proposed solutions can maintain circuit stability: physical leakage compensation can be a general approach while virtual leakage compensation offers higher energy efficiency and lower cost, but its applications are limited by some factors.

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