Design and energetic characterization of a proportional-injector monopropellant-powered actuator

This paper describes the design and energetic characterization of an actuator designed to provide enhanced system energy and power density for self-powered robots. The proposed actuator is similar to a typical compressible gas fluid-powered actuator, but pressurizes the respective cylinder chambers via a pair of proportional injector valves, which control the flow of a liquid monopropellant through a pair of catalyst packs and into the respective sides of the double-acting cylinder. This paper describes the design of the proportional injection valves and describes the structure of a force controller for the actuator. Finally, an energetic characterization of the actuator shows improvement relative to prior configurations and marked improvement relative to state-of-the-art batteries and motors.     

Modeling,control, and analysis of a robotic assist device

This paper presents a model-based approach to control design for an existing lower-limb robotic assist device, the portable powered ankle–foot orthosis (PPAFO). This approach seeks to address two key limitations of the PPAFO caused by the use of solenoid valves: slow system response and inefficient actuation during assistance. System limitations were addressed using a proportional valve coupled with a modified control approach. The two different system configurations were compared in simulation and on an experimental test fixture during motion and torque control tasks. Root mean square (RMS) trajectory tracking error was used to evaluate system performance, while system efficiency was assessed by measuring pneumatic fuel consumed during each task. The proportional valve system reduced RMS tracking error by as much as 91%, and increased efficiency by as much as 95% over the solenoid valve system.     

Position control of hybrid pneumatic–electric actuators using discrete-valued model-predictive control

The design, modeling and position control of a novel hybrid pneumatic–electric actuator for applications in robotics and automation is presented. The design incorporates a pneumatic cylinder and DC motor connected in parallel. By avoiding the need for a high ratio transmission, the design greatly reduces the mechanical impedance that can make collisions with conventionally actuated robot arms dangerous. A novel discrete-valued model-predictive control (DVMPC) algorithm is proposed for controlling the position of the pneumatic cylinder with inexpensive on/off solenoid valves. A variant of inverse dynamics control is proposed for the DC motor. A prototype was built for validating the actuator design and control algorithms. It is used to rotate a single-link robot arm. The actuator inertia and static friction torque values for the prototype were only 0.6% and 4%, respectively, of the values found for a comparable actuator from an industrial robot. Simulation results for position control of pneumatic actuators with different valve speeds and friction coefficients show that the DVMPC algorithm outperforms a sliding mode control algorithm in terms of position error and expected valve life. Experimental results are presented for vertical rotary cycloidal trajectories. Even with the poor quantization caused by the on/off valves, the pneumatic cylinder controlled by the proposed DVMPC algorithm achieved a 0.7% root mean square error (RMSE) and a 0.25% steady-state error (SSE). With the addition of the DC motor to form the hybrid actuator, the RMSE and SSE were reduced to 0.12% and 0.04%, respectively. By incorporating a novel estimation algorithm, the system was made robust to an unknown payload.     

Accurate position control of a pneumatic actuator using on/offsolenoid valves

The development of a fast, accurate, and inexpensive position-controlled pneumatic actuator that may be applied to a variety of practical positioning applications is described. A novel pulse width modulation (PWM) valve pulsing algorithm allows on/off solenoid valves to be used in place of costly servo valves. The open-loop characteristic is shown both theoretically and experimentally to be near symmetrical. A comparison of the open- and closed-loop responses of standard PWM techniques and that of the novel PWM technique shows that there has been a significant improvement in the control. A linear process model is obtained from experimental data using system identification. A proportional integral derivative controller with added friction compensation and position feedforward has been successfully implemented. A worst case steady-state accuracy of 0.21 mm was achieved with a rise time of 180 ms for step inputs from 0.11 to 64 mm. Following errors to 64-mm S-curve profiles were less than 2.0 mm. The controller is robust to a sixfold increase in the system mass. The actuator's overall performance is comparable to that achieved by other researchers using servo valves     

A piezoelectric driven ratchet actuator mechanism with application to automotive engine valves

Increasing demands on the performance of internal combustion engines, specifically automobile engines, require the production of more mechanical energy for a given amount of chemical fuel with reduced tailpipe emissions. Of particular interest in the development of high performance/low emission engines is the control and timing of individual engine valves. This paper investigates the design of an innovative piezoelectric ceramic (PZT) based actuator mechanism with a novel stepping motion amplifier to deliver force and displacement at higher magnitudes and operating frequencies. The target application is an engine valve train which traditionally uses cam-based lifter driven rocker arms to regulate the cylinders’ intake and exhaust valve motion. The proposed PZT-based actuator mechanism introduces a high frequency, lightweight, precise position solution for cylinder-by-cylinder variable valve timing. Numerical results are provided to demonstrate the feasibility of a PZT-based/camless valve train. The new valve train demonstrates similar cam-based performance characteristics while enabling computer controlled individual valve timing opportunities.     

Control of an air pressure actuated disposable bioreactor for cultivating heart valves

A disposable injection molded bioreactor for growing tissue-engineered heart valves is controlled to mimic the physiological heart cycle. Tissue-engineered heart valves, cultured from human stem cells, are a possible alternative for replacing failing aortic heart valves, where nowadays biological and mechanical heart valves are used. Growing and conditioning is done by mechanically stimulating the tissue in a bioreactor. The disposable injection molded bioreactor uses flexible membranes and steering valves to mimic a physiological heart cycle. In this work, an air pressure actuation control system for this bioreactor is designed. One membrane is position controlled to achieve a desired flow through the heart valve, while another membrane controls the aortic pressure. A third actuator controls a steering valve used to impose a resistance on the flow back to the first membrane, in order to control the heart valve closing pressure. Due to the repetitive character of the setpoints, repetitive controllers are designed and implemented. A high position tracking performance is achieved and pressure setpoints are mimicked successfully, while preventing large pressure oscillations and suppressing disturbances that could be damaging for the tissue heart valve. The control system allows full adjustability of operating conditions needed for the growing, conditioning and testing phases of tissue engineered heart valves.     

基于虚拟仪器的高速电磁开关阀动态特性研究

高速电磁阀在控制系统中的应用越来越广泛,其动态特性直接影响了系统的性能。为了研究电磁阀的动态性能,从电磁阀的结构入手,详细分析了其工作原理,得到了工作电流曲线模型。通过设计驱动电路,并且利用虚拟仪器技术,对电磁阀的工作电流进行了测试,得到了实际的电流曲线。结果表明,利用虚拟仪器搭建的系统能对电磁阀的动态特性进行有效地测试。     

Development of a high-speed solenoid valve: investigation ofsolenoids

The authors have developed a high-speed solenoid valve with a 1 ms switching time to control diesel engines electronically. In this paper, the authors focused their attention on developing the solenoid itself, investigating methods to be used for the fast operation of the solenoid valve. First, by using a mathematical model, they quantitatively examined the effects of design particulars, such as the dimensions of the solenoids and the number of turns of coil, on the switching time. According to the results obtained by the above examinations, they studied an effective method for fast switching. Next, they investigated appropriate and comprehensive methods that would satisfy given specifications under the various restrictions inherent in the solenoid valve's operation. In the final stage, they manufactured solenoid valves in accordance with the investigated methods, and evaluated their performance     

Accurate Sliding-Mode Control of Pneumatic Systems Using Low-Cost Solenoid Valves

A control law is developed for an inexpensive pneumatic motion control system using four solenoid on/off valves and a position feedback sensor. A sliding-mode approach is used, which is well known for its tolerance for system uncertainties. In contrast to previous control laws, our approach does not use pulsewidth modulation. The control law has an energy-saving mode that saves electrical power, reduces chattering, and prolongs the valve's life. Our simulation and experimental results show that the proposed tracking control law performs very well with good tracking and relatively low steady-state position errors     

New polarized electromagnetic actuators as integrated mechatronic components — design and application

This paper presents an overview over the computer-aided design process of mechatronic devices and systems, especially the design of electrodynamic and electromagnetic drives using modern high-energy permanent magnetic materials like NdFeB and SmCo. This paper also presents some examples of such actuators. The first example is a miniaturized pneumatic valve for industrial applications. This valve has an integrated bi-stable polarized solenoid actuator. The second example is a polarized electromagnetic valve manufactured by modern batch technologies using photo-structurable glass material. The valve seat and the actuator coils are realized using this glass material. The third example is a gripping device with compliant mechanism and planar moving coil actuator.     

涡轮增压器废气旁通换向电磁阀优化设计与分析

本文以涡轮增压器中的废气旁通换向电磁阀为例,对该电磁阀的优化设计问题进行了分析,首先对废气旁通换向电磁阀进行了概述,继而从整体设计以及电磁铁的优化设计两个角度对其优化设计过程进行了讨论,最后研究了其在未来的发展方向,目的在于使其在应用过程中存在的问题能够被有效的解决,达到增加发动机输出功率的目的,为涡轮增压器性能的改善带来更大的价值.     

Development of a high-speed solenoid valve-investigation of theenergizing circuits

The electrical circuits developed for the purpose of energizing the solenoid valve are examined. These circuits, called the dummy coil method, where energy stored in a dummy coil in the form of a magnetic field is transferred to an energizing solenoid, and the pre-energize method, where the solenoid is electrically energized in advance by taking advantage of the solenoid's attraction force characteristics, are discussed. The results of experiments show that the pre-energize method is highly effective in speeding up the operation of solenoid valves. These experimental results are discussed along with the results of calculations conducted using a mathematical model     

A fast, digitally controlled flow proportional gas injection system for studies in lung function

The aim of this paper is to describe a device for flow proportional injection of tracer gas in the lungs of mechanically ventilated patients. This device may then be used for the study of the multiple breath indicator gas washout technique to determine the end-expiratory lung volume. Such a tracer gas injection device may also be used in the study of other techniques that rely on uptake and elimination of tracer gas by the lungs. In this paper, an injector is described which enables injection of indicator gas at a predetermined concentration in a breathing circuit independent of the type of breathing. The presented setup uses a control computer to produce steering signals to a multivalve array in proportion to the input breathing signals. The multivalve array consists of ten circular valves, each with a different diameter, which can be opened or closed individually according to the input signal of the array. By opening of a certain combination of valves an amount of sulphur hexafluoride gas proportional to the inspiratory breathing signal is released. The rate of transmission between the components of the injection system was 80 Hz. The injector has a full flow range between 0-10 L/min. The delay time between the breathing signal and the flow response was 70 ms. The aimed washin gas concentration of 1% SF6 was achieved after 0.5 s. The study describes the results of tests to determine valve-flow ratios, step response and dynamic response of the injector. The flow output response of the injector system was shown to increase in input frequencies above 3 Hz. The valve flow ratios showed the largest relative deviation in the two smallest valves of the 10 valve array, respectively 0.005 L/min (25%) and 0.002 L/min (20%). We conclude that the injector can achieve a stable concentration of indicator gas in a breathing system with an accuracy of 0.005 L/min to execute the multiple breath indicator washout test in human subjects. The results of the study indicate that the injector may be of use in other application fields in respiratory physiology in which breathing circuit injection of indicator gas is required.     

Development of a new fully flexible hydraulic variable valve actuation system for engines using rotary spool valves

In this paper, a new hydraulic variable valve actuation (VVA) system is proposed and designed. The VVA system can significantly improve the engine performance in terms of the power density, volumetric efficiency, emission, and fuel consumption. In this system, each engine valve is actuated by a hydraulic cylinder which is charged and discharged using two rotary spool valves. The rotary spool valves are rotated by the engine crankshaft while their phases are controlled by hydraulic or electric phase shifters. Similar to camless valvetrains, the new engine valve system is capable of flexible engine valve timing and lift at any engine speed without the drawbacks of existing camless valvetrains including high control complexity, low reliability, and slow actuator response. The mathematical model of the system is derived and verified by comparing simulation and experimental results. Two feedback controllers are designed and implemented for precise valve opening and closing timing and valve lift control. Experiments are performed to validate the mathematical model and evaluate the proposed system's performance. The results show excellent system repeatability and controllability at different operating conditions.     

Fractional order control to the electro-hydraulic system in insulator fatigue test device

In this paper, a special composite hydraulic cylinder, which includes two pistons and three working chambers, is proposed for driving the insulator fatigue test device. In this force loading system, a servo valve and a proportional pressure valve are used to control the composite hydraulic cylinder to generate alternating force and fixed force respectively. Furthermore, the models of the electro-hydraulic system are built and its dynamic characteristic is analyzed based on the models. Considering the uncertainty of the model parameters, the fractional order proportional-integral-derivative controller is adopted to control the two valves. The Oustaloup method is used to discrete the fractional order controller and the iteration feedback tuning method is presented to tune the controller parameters. The tuning process which is independent on the system model can be done on the close loop system. Simulation and experimental results have shown that the fractional order controller is effective.     

High-gain observer-based pump/valve combined control for heavy vehicle electro-hydraulic servo steering system

Electro-hydraulic servo steering system (EHSSS) has been widely used in multi-axle heavy vehicles. Noteworthy, the traditional EHSSS controlled only by servo solenoid valve has amounts of energy loss in throttling orifice. Although the steering control accuracy is ensured, it leads to low energy efficiency. In this paper, a novel pump/valve combined control (PVCC) EHSSS is proposed to increase the energy efficiency, which only uses one servo motor pump and one servo solenoid valve to drive the steering trapezoid mechanism. Based on the control objectives of low pressure difference in valve orifice and high steering tracking performance, a dual-input-dual-output control strategy is proposed. To guarantee the high steering tracking performance of PVCC steering system, a high-gain observer based sliding mode controller (HGO-SMC) is designed for controlling the spool displacement of servo solenoid valve. During the steering process, the servo motor pump is controlled by a simple speed feedforward and PID controller, so that the pressure difference in throttling orifice is kept at a low value to reduce the energy wasted. The experimental comparison results show that the proposed method can achieve the same tracking performance as valve control EHSSS with less energy consumption.     

太阳能与空气能双热源热泵系统实验平台设计

为解决太阳能和空气能利用中存在的能量转换效率低的问题,设计了太阳能与空气能双热源热泵系统实验平台.实验平台主要由变频压缩机、PV/T蒸发器、风冷蒸发器、蓄热水箱、电子膨胀阀、数据采集与控制系统等组成,以太阳能和空气能作为热源,R134a作为制冷工质,通过控制电磁阀和电子膨胀阀,实现3种运行模式.利用PLC和组态软件实现...     

基于FPGA的电磁阀控制设计与研究

针对航空飞行器在飞行试验中需要精确控制滚控发动机电磁阀的难题,从电磁阀自身特点入手,设计了控制硬件电路并建立电磁阀门硬件电路灭弧电路响应时间模型,成功卸载60.5V反向大电压,详细分析影响电磁阀的时间因素,同时也提出了基于FPGA的电磁阀可配置脉冲的实现方式。目前,该电磁阀控制设计已成功应用于地面发动机测试设备,具有较好的实时性、安全性和时间响应性能。     

压电执行器及其在液压阀中的应用

以压电执行器为核心的高速开关阀及伺服阀等压电式液压阀具有频响高,微动性能好,结构紧凑等优点,是新型阀控类型之一,受到国内外研究者的持续关注。首先,该文介绍了阀用压电执行器的分类和特点,根据工作原理分为直推式和步进式2类4种形式;其次,对先导型、直动型、喷嘴挡板型和开关型4种典型压电阀的研究进展进行了梳理,分析了各自的代表性结构、性能特点。结果表明,随着未来对液压阀精密化、智能化需求的提升,压电液压阀的应用前景更广。因此,除高性能介电材料开发外,如微位移放大、迟滞补偿控制等关键压电驱动与控制技术仍有待深入研究。     

高速电磁阀在自适应单车试验系统中的应用

单车试验系统是模拟火车刹车时列车底部列管的排风减压过程,进而对火车制动机进行检测的工具。随着新型车辆的研制,车辆列管容积不断发生变化,原有系统已不能适应新型车辆的检测要求。自适应单车试验系统利用经典PID控制理论,通过对脉宽调制式高速电磁阀的控制,使各种列管容积的车型试验排风曲线都很好地跟踪标准压力曲线,达到了铁道部对制动机进行试验要求。