Andrew R. Plummer

Andrew R. Plummer
University of Bath | UB · Department of Mechanical Engineering

PhD

About

164
Publications
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3,168
Citations

Publications

Publications (164)
Article
With the intensification of energy shortages and environmental pollution, new energy sources represented by wind and solar energy have received global attention. Although the proposal of hydraulic wind turbines effectively solves the problems of traditional wind turbine transmission impact and complicated installation and maintenance, further explo...
Article
The switched inertance hydraulic converter is a sub-domain of digital hydraulics which relies on digital switching to adjust pressure or flow instead of the dissipation of power by throttling, providing an energy-efficient alternative to conventional proportional or servo valve-controlled systems. The high-speed switching valve is a key component t...
Article
Real‐time hybrid testing involves the separation of a system into an experimental component and a numerically simulated substructure which are coupled and run together. The coupling between substructures is achieved using actuators and force sensors which comprise the transfer system. Close synchronization is required between substructures for reli...
Conference Paper
Pneumatic artificial muscles (PAMs) are high power-to-weight ratio actuators with considerable potential in biomimetic robotics and orthotics due to their similarities with human skeletal muscle. However, precise position control is difficult to achieve due to the highly nonlinear nature of the actuators and the pneumatic systems driving them. A wi...
Conference Paper
Hydraulic manifolds are traditionally manufactured using externally drilled intersecting galleries. This results in undesirable artefacts in the flow path such as sharp corners, and dead oil volumes, and requires additional plugs to blank redundant holes. These artefacts affect flow separation, aggravate pressure-drop and reduce hydraulic stiffness...
Conference Paper
Switched inertance hydraulic converters (SIHC) are new digital hydraulic devices which provide an alternative to conventional proportional or servo valve-controlled systems in hydraulic fluid power. SIHCs can adjust and control flow and pressure by means of using digital control signals that do not rely on throttling the flow and dissipation of pow...
Article
Full-text available
This paper is a thorough review of innovative architectures of electro-hydraulic servovalves that exploit actuation systems based on piezo-electric materials. The use of commercially available piezo-electric actuators, namely, piezo stacks, amplified piezo stacks, rectangular benders, and ring benders, is very promising for the actuation of the mai...
Article
Full-text available
This paper presents a feasibility study using commercially available amplified piezo-stacks for the direct actuation of four-way three-position (4/3) direct drive servovalves. The prospect of using amplified piezo-stacks in place of linear force motors is very attractive by virtue of their fast response speed and low weight. Piezo-stacks equipped w...
Preprint
Full-text available
This paper is a thorough review of innovative architectures of electro-hydraulic servovalves that exploit actuation systems based on piezo-electric materials. The use of commercially available piezo-electric actuators, namely, piezo-stacks, amplified piezo-stacks, rectangular benders and ring benders, is very promising for the actuation of the main...
Conference Paper
Piezo pumps provide an attractive alternative for driving small actuators (e.g. less than 100W) compared to traditional valve controlled cylinders powered by a central hydraulic supply. This provides the ability to distribute power electrically rather than hydraulically, which can bring both weight and efficiency savings. Currently the use of piezo...
Article
Full-text available
Human Locomotion Mode Recognition (LMR) has the potential to be used as a control mechanism for lower-limb active prostheses. Active prostheses can assist and restore a more natural gait for amputees, but as a medical device it must minimize user risks, such as falls and trips. As such, any control system must have high accuracy and robustness, wit...
Article
Modern aircraft wings change shape via the deflection of discrete, hinged, control surfaces, which often exhibit areas of adverse pressure gradient along the hinge line, leading to flow separation and poor wing efficiency. To reduce surface discontinuities and sharp edges, a possible solution is to replace part of the conventional wing with a smart...
Article
Back-stepping design method is widely used in high-performance tracking control tasks As is known to all, the controller based on back-stepping design will become complex as the model order increases, which is the so called “explosion of terms” problem. In this paper, a tracking differentiator (TD) based back-stepping controller is proposed to hand...
Article
Fluid-borne noise (FBN) is a major contributor to structure-borne noise (SBN) and air-borne noise (ABN) in hydraulic fluid power systems and could lead to increased fatigue in system components. FBN is caused by the unsteady flow generated by pumps and motors and propagates through the system resulting in SBN and ABN. New hydraulic technologies suc...
Article
Full-text available
Despite being widely used in several applications, commercially available spool valves, both servovalves and proportional valves, are inefficient components because they cause high power consumption due to the large pressure drops across the metering orifices. A recent research field aims at substituting spool valves with on/off valves having high...
Article
Full-text available
Background With large numbers of COVID-19 patients requiring mechanical ventilation and ventilators possibly being in short supply, in extremis two patients may have to share one ventilator. Careful matching of patient ventilation requirements is necessary. However, good matching is difficult to achieve as lung characteristics can have a wide range...
Article
Full-text available
Optimal control strategies represent a widespread solution to increase the extracted energy of a Wave Energy Converter (WEC). The aim is to bring the WEC into resonance enhancing the produced power without compromising its reliability and durability. Most of the control algorithms proposed in literature require for the knowledge of the Wave Excitat...
Article
The requirement for An electrical grid-connected wind turbine is that the synchronous generator speed is stable within a required speed range for the electrical grid. In this paper, a hydraulic wind turbine (HWT) system is considered, and the working principle and working conditions of the HWT are introduced. A novel speed control method is propose...
Article
Full-text available
In real-time hybrid testing, systems are separated into a numerically simulated substructure and a physically tested substructure, coupled in real time using actuators and force sensors. Actuators tend to introduce spurious dynamics to the system which can result in inaccuracy or even instability. Conventional means of mitigating these dynamics can...
Conference Paper
Hydraulic servos are characterised by their high-performance nature but due to their size and weight are not suitable for robotics where new legged applications require high power density and excellent dynamic behaviour in a small size. As an answer to this need a new class of integrated smart actuators is being developed. These systems consist of...
Article
The power captured by a wave energy converter (WEC) can be greatly increased through the use of a well-conceived wave-by-wave control strategy. Optimal strategies including Model Predictive Control (MPC) rely on a dynamic model of the WEC and prediction of the wave excitation force several seconds into the future. Both the modelling and prediction...
Article
Full-text available
Soft robots and devices exploit deformable materials that are capable of changes in shape to allow conformable physical contact for controlled manipulation. While the use of embedded sensors in soft actuation systems is gaining increasing interest, there are limited examples where the body of the actuator or robot is able to act as the sensing elem...
Article
Full-text available
This article presents a novel passivity-based adaptive delay compensation scheme for cancelling actuator dynamics in real-time hybrid testing. This scheme uses the energy added to the system by actuation hardware, to quantify a variable delay, which is subsequently used for delay compensation. It offers the advantage of correcting for tracking erro...
Article
Real-time hybrid testing is a technology which allows the coupling of simulations and component tests in order to simulate complex system dynamics. Delays and time lags caused by actuator dynamics and signal processing deteriorate the stability of the tests in many cases. The application of adaptive feedforward filters to hybrid testing enables cir...
Article
An active control strategy is a key component to enable efficient, safe and economical operation of a wave energy converter (WEC). Many strategies have been developed, but most studies are limited to simplified simulation models of WECs which are not representative of real devices. Furthermore, many studies assume perfect knowledge of the wave exci...
Article
Full-text available
In part I of this study, we experimentally and numerically investigated the pilot stage of a novel two-stage servovalve architecture. The novelty of the proposed configuration is the torque motor being removed and replaced with two small two-way two-position (2/2) valves actuated by piezoelectric ring benders, which can effectively control the open...
Article
Digital hydraulics is a new technology providing an alternative to conventional proportional or servovalve-controlled systems in the area of fluid power. Digital hydraulic applications, such as digital pumps, digital valves and actuators, switched inertance hydraulic converters (SIHCs) and digital hydraulic power management systems, promise high-en...
Preprint
Full-text available
Objectives With large numbers of COVID-19 patients requiring mechanical ventilation and ventilators possibly being in short supply, in extremis two patients may have to share one ventilator. Careful matching of patient ventilation requirements is necessary. However, good matching is difficult to achieve as lung characteristics can have a wide range...
Article
Real-time hybrid testing combines the reliability of experimental testing with the convenience of numerical simulation. The system to be tested is split into a physical substructure and a real-time numerical simulation which are coupled using actuators and sensors to transfer data at the interface in real-time. In order to achieve stable and accura...
Article
Structures and actuation systems need to be closely integrated together in the future to create faster, more efficient, lightweight dynamic machines. Such actuated structures would be used for morphing aircraft wings, lightweight actuated space structures, or in robotics. This approach requires actuators to be distributed through the structure. A t...
Article
Full-text available
The switched inertance hydraulic converter (SIHC) is a new technology providing an alternative to conventional proportional or servo-valve-controlled systems in the area of fluid power. SIHCs can adjust or control flow and pressure by means of using digital control signals that do not rely on throttling the flow and dissipation of power, and provid...
Article
Full-text available
Electrohydraulic servovalves are widely used for precise motion control in aerospace and other industries due to their high accuracy and speed of response. However, commercial two-stage servovalves have several undesirable characteristics, such as the power consumption caused by the quiescent flow (internal leakage) in the pilot stage, and the comp...
Article
Full-text available
In this paper, we investigate the idea of using, in place of recent linear force motors, amplified piezo-stack actuators for the actuation of direct drive servovalves, in order to exploit the fast response of piezoelements accompanied by the increased displacement ensured by mechanical amplification systems. Some possible architectures are proposed...
Article
Full-text available
This paper proposes a modelling approach for simulating mechanical ventilators for intensive care units (ICUs). The shortage of ventilators during the coronavirus disease 2019 (COVID-19) pandemic has focused attention on their design and performance. The proposed modelling approach consists in using the Mathworks ® Simulink software tool and the Si...
Article
A well-conceived real-time control strategy can greatly increase the captured power for a wave energy converter (WEC). Optimal strategies rely on a dynamic model of the WEC and prediction of the wave excitation force several seconds into the future. Both the modelling and prediction processes are subject to errors. This paper investigates the impac...
Conference Paper
The internal leakage in two stage servovalves causes unwanted power consumption; it is the sum of two contributions: the internal leakage in the main stage and the internal leakage in the pilot stage. While the latter can be assumed almost constant regardless of the spool position, the former is maximum at null and decreases with increasing opening...
Conference Paper
A fundamental component of two-stage servovalves is the flexure tube, since it both constitutes a low friction pivot for the inner flapper and allows the torque motor to be separated from the hydraulic fluid, thus avoiding contamination particles being trapped inside the torque motor. The inertia of the torque motor armature interacting with the fl...
Conference Paper
Full-text available
This paper presents research aimed at understanding the effects of geometrical imperfections and tolerances upon the internal leakage occurring around null in the main stages of servovalves. Specifically, a two-dimensional (2D) computational fluid dynamic analysis was used to predict the direct leakage flow as a function of the overlap and clearanc...
Article
Electro-hydraulic shaking tables are widely used for vibration testing where high force and displacement amplitudes are required. In particular, they are a vital tool in seismic testing, enabling the development of buildings and other structures which are earthquake resistant. Three-variable-control (TVC) is commonly used for the control of multi-d...
Chapter
Legged robots are dynamic moving machines that are potentially able to traverse through rough terrain which is inaccessible for wheeled or tracked vehicles. For bipedal robots, balancing control while hopping/running is challenging, especially when the foot contact area is small. Servo hydraulics is highly suitable for robot leg actuation due to it...
Article
This paper presents a prototype powered ankle prosthesis which can operate passively in most of the gait cycle and provide powered assistance for toe push-off and subsequent foot dorsiflexion. The use of electrohydrostatic actuation (EHA) gives the ability to switch quickly and smoothly between passive and active modes. In this new powered ankle pr...
Article
Full-text available
This paper provides a review of the state of the art of electro-hydraulic servovalves, which are widely used valves in industrial applications and aerospace, being key components for closed loop electrohydraulic motion control systems. The paper discusses their operating principles and the analytical models used to study these valves. Commercially...
Article
This paper provides a review of the state of the art of electro-hydraulic servovalves, which are widely used valves in industrial applications and aerospace, being key components for closed-loop electro-hydraulic motion control systems. The paper discusses their operating principles and the analytical models used to study these valves. Commercially...
Conference Paper
Digital hydraulics is a new technology providing an alternative to conventional proportional or servovalve-controlled systems in the area of fluid power. Research is driven by the need for highly energy efficient hydraulic machines but is relatively immature compared to other energy-saving technologies. Digital hydraulic applications, such as digit...
Conference Paper
Full-text available
This paper proposes a novel architecture for the pilot stage of electro-hydraulic two-stage servovalves that does not need a quiescent flow and a torque motor as well as a flexure tube to operate. The architecture consists of two small piezoelectric valves, coupled with two fixed orifices, which allow variation of the differential pressure at the m...
Conference Paper
This paper presents the design and control of a morphing wing structure using an active tensegrity structure. A tensegrity structure, which is a set of compressive members (struts) stabilized by a set of tensile members (cables) is a good basis for creating a lightweight active structure, due to its potentially high stiffness-to-weight ratio, and t...
Article
Full-text available
This paper reviews the state of the art of directly driven proportional directional hydraulic spool valves, which are widely used hydraulic components in the industrial and transportation sectors. First, the construction and performance of commercially available units are discussed, together with simple models of the main characteristics. The revie...
Article
This paper develops a detailed simulation model, realized by the software Simscape, which can be a powerful tool to analyze the performance of a double nozzle flapper valve actuated by a piezoelectric ring bender. The particularity of this valve is that the use of the torque motor and flexure tube is avoided, thus reducing the complexity, manufactu...
Conference Paper
In the legged locomotion research area, it is known that efficient running or hopping in either animals or legged robots requires leg actuator compliance. Springy legs interacting with body mass gives a natural hopping/running frequency. Servo-hydraulics is highly suitable for robot leg actuation due to its high power density and fast response. In...
Article
Full-text available
Oscillating surge wave energy converters (OSWECs) offer the possibility to convert ocean wave energy in the near shore region into electricity. One of the unique challenges they present is that the forces experienced in each direction differ. The curved geometry of the CCell device exaggerates this difference. Presented in this paper is a novel met...
Chapter
The power take‐off (PTO) converts the power available at the primary wave interface, often mechanical power associated with the movement of a float or paddle, into electrical power. This chapter provides an introduction to electrical generators, which transform mechanical to electrical power, both rotary and linear. The rotary generator technology...
Article
This paper reviews recent developments in digital switched hydraulics particularly the switched inertance hydraulic systems (SIHSs). The performance of SIHSs is presented in brief with a discussion of several possible configurations and control strategies. The soft switching technology and high-speed switching valve design techniques are discussed....
Conference Paper
This paper introduces the simulation of a wave-to-wire (W2W) wave energy converter (WEC) design that includes the complete system from the original wave capture device to the final generated electricity supplied to the grid. Instead of designing the sub-systems separately, this holistic approach allows the optimization of the WEC performance. The E...
Conference Paper
For smaller-capacity WECs, array deployment is perceived as being the most likely way for grid-scale deployment to be approved. However, the understanding of the hydrodynamic interactions within such arrays, especially for devices with non-conventional modes of oscillation, is still at an early stage. In the present work, a CFD simulation is develo...
Conference Paper
The Power TakeOff (PTO) is an integral part of all Wave Energy Converters (WECs). As well as fulfilling its primary purpose of extracting power from the WEC it is frequently the main control member within the device too. This means that its dynamic response can be as important as its efficiency in governing Levelised Cost of Energy (LCoE) as this d...
Conference Paper
Hardware-in-the-Loop (HIL) testing has been used successfully for a number of years on a wide range of applications. Any delay in actuation systems will increase the system energy if it is not properly compensated for due to the negative damping effect. A HIL walking/running testing system has advantages for testing lower-limb prosthetics over trad...
Article
Full-text available
This paper addresses the problem of controlling the hopping height and stride length of a monoped hydraulic robot. Hopping over discontinuous, rough terrain with limited surfaces suitable for foot placement requires a controller capable of adjusting the hop height and landing foot position of the robot on each step. This motivates the need for an a...