Mechatronic Actuator Research Articles

Measurement System for the Calibration of Accelerometer Arrays

This paper addresses accelerometer array calibration, focusing on determining the errors between multiple sensors. Micro-electromechanical system (MEMS) based triaxial accelerometers, key components of Inertial Measurement Units (IMUs), are used in localization, robotics, and navigation systems. The requirements of these applications necessitate low-cost sensors, which makes MEMS IMUs a reasonable choice. However, these low-cost IMUs are significantly affected by systematic (i.e., bias, misalignment, scale-factor) and random errors. Achieving reliable sensor output depends on the precision of the executed calibration method. While traditional laboratory-based sensor calibration using specialized equipment (i.e., three-axis turntable) is accurate, it is time-consuming and costly. In contrast, in-field calibration techniques, which can be performed using a mechatronic actuator or a robotic arm, have gained popularity. These techniques involve comparing sensor measurements to established reference values. The MEMS sensors are increasingly being used in multi-sensor applications, which demands not only individual sensor error calibration but also important to determine the axis misalignment between the used sensors. During calibration process, various optimization algorithms (e.g., GA, PSO) can also be used to find the error parameters. The proposed measurement system allows for individual calibration of misalignment, bias, and scale factor of the sensor array, and eliminates between-sensor misalignment errors.

Improving Walking Energy Efficiency in Transtibial Amputees Through the Integration of a Low-Power Actuator in an ESAR Foot.

Reducing energy consumption during walking is a critical goal for transtibial amputees. The study presents the evaluation of a semi-active prosthesis with five transtibial amputees. The prosthesis has a low-power actuator integrated in parallel into an energy-storing-and-releasing foot. The actuator is controlled to compress the foot during the stance phase, supplementing the natural compression due to the user's dynamic interaction with the ground, particularly during the ankle dorsiflexion phase, and to release the energy stored in the foot during the push-off phase, to enhance propulsion. The control strategy is adaptive to the user's gait patterns and speed. The clinical protocol to evaluate the system included treadmill and overground walking tasks. The results showed that walking with the semi-active prosthesis reduced the Physiological Cost Index of transtibial amputees by up to 16% compared to walking using the subjects' proprietary prosthesis. No significant alterations were observed in the spatiotemporal gait parameters of the participants, indicating the module's compatibility with users' natural walking patterns. These findings highlight the potential of the mechatronic actuator in effectively reducing energy expenditure during walking for transtibial amputees. The proposed prosthesis may bring a positive impact on the quality of life, mobility, and functional performance of individuals with transtibial amputation.

In-Mould OCT Sensors Combined with Piezo-Actuated Positioning Devices for Compensating for Displacement in Injection Overmoulding of Optoelectronic Parts

When overmoulding optoelectronic devices with optical elements, precise alignment of the overmoulded part and the mould is of great importance. However, mould-integrated positioning sensors and actuators are not yet available as standard components. As a solution, we present a mould-integrated optical coherence tomography (OCT) device that is combined with a piezo-driven mechatronic actuator, which is capable of performing the necessary displacement correction. Because of the complex geometric structure optoelectronic devices may have, a 3D imaging method was preferable, so OCT was chosen. It is shown that the overall concept leads to sufficient alignment accuracy and, apart from compensating for the in-plane position error, provides valuable additional information about the sample both before and after the injection process. The increased alignment accuracy leads to better energy efficiency, improved overall performance and less scrap parts, and thus even a zero-waste production process might be feasible.

An optimized excitation signal design for identification of PWA model and application to automotive throttles

In the automotive application for Electronic Control Units (ECU), dynamic models with high-precision to simulate mechatronic actuators are required for various analysis and design tasks like Hardware-in-the-Loop (HiL) simulation. It is known that the modeling of systems with significant friction effects is not accessible. The piecewise-affine (PWA) model has recently attracted considerable interest due to its high approximation capability for modeling systems with friction. Because the model quality depends intensely on the test signal design, a model-free optimized excitation signal design for identifying PWA models is presented in this paper. The presented method is demonstrated with an automotive throttle, and a PWA model is identified with a four-step identification approach. The result shows that the optimization method can achieve a better model quality, which is sufficient for the HiL simulation.

Untersuchung des anwendungsnahen, dynamischen Reibverhaltens nasslaufender Lamellenkupplungen am Beispiel zweier Tribosystemvarianten

In order to be able to design the tribological system in a targeted way for use as a mechatronic actuator, e.g. for influencing vibration-dynamic properties, knowledge of the friction behavior occurring in the application is necessary. The method described in this paper supports the characterization of the dynamic, application-related friction behavior of a wet-running multi-plate clutch. This enables more accurate and in particular, application-related predictions of behavior in wet-running friction contact, such as the transmissible torque in dynamic operation with adjusted tribological systems. It supports the early stage design of functional extensions in the wet-running clutch system. In this paper, the method is used with two tribological system variants that vary in their friction lining. Differences in their dynamic friction coefficient behavior were identified.

Numerically Efficient Discrete-Time Dielectric Elastomer Actuators Models for Optimal Control

Dielectric elastomers can be used to develop innovative mechatronic actuators (called DEA). In this paper, we consider the optimal control problem (OCP) of transitioning between an actuator's operating states. Following a model-based approach, a set of discrete-time state equations is derived for the DEA, which satisfy accuracy demands and, at the same time, can be solved efficiently by numerical methods. Due to numerical stiffness, the implicit midpoint rule is chosen as an integration method. Then, we discuss different classes of input signals to be considered in the OCP. In particular, zero-order-hold and first-order-hold parametrizations are compared within the OCP formulation. While we show equivalence of two OCP formulations from the theoretical point of view, numerical investigations show benefits of our proposed OCP model regarding the quality of computed solutions and the robustness w.r.t. initial guesses. Altogether, we derive a numerically treatable DEA optimal control set-up, which can be used for various control tasks.

EFFECT OF WIRE ELECTRICAL DISCHARGE MACHINING ON THE SURFACE OF EBM-ADDITIVE MANUFACTURED NITI ALLOYS

Nickel-titanium (NiTi) shape memory alloys are used in varied engineering products, such as biomedical device and mechatronic actuator applications. The conventional machining technology are utilized in the limited fields due to their effects on the hardness and brittleness of the machined alloys. However, the wire electrical discharge machining (WEDM) technology is one of the most preferred post-processing tool to obtain a surface with high quality. The electrical current and voltage values with pulse on and pulse off time are the crucial parameters for WEDM. These parameters should be optimized before wire electrical discharge machining process. Electron beam melting (EBM)-based additive manufacturing of the nickel-titanium powders provides obtaining bulk NiTi shape memory alloys using high energy electron beams. In this study, the application of WEDM which is used as a post-processing tool is evaluated for the EBM-based additive manufactured NiTi samples. Additionally, the scanning electron microscopy results of the wire electrical discharge machined NiTi samples are carefully investigated.

Influence of spatially varying material properties on the bimoment normal and shear stresses by warping torsion of FGM beams

In this contribution, which is an extension of author’s research [1,2], an influence of the in two and three directions varying material properties on non-uniform torsion of the Functionally Graded Material (FGM) thin-walled beams is originally investigated. Based on the semi-analytical solution of the fourth order differential equation for non-uniform torsion, the local finite element equations of the twisted FGM beam are presented, considering the non-uniform torsion with effect of warping and secondary deformations due to the angle of twist. The warping part of the first derivative of the twist angle caused by the bimoment is considered as an additional degree of freedom at the beam nodes. The Multi-Layers Method (MLM) [3], and the Reference Beam Method (RBM) [4] are extended for homogenization of the spatially varying material properties and relevant stiffnesses in the real beam onto effective longitudinally varying ones in the homogenized beam for the load case of non-uniform torsion.The focus of the numerical investigation, with consideration of the warping and Deformation Effect due to the Secondary Torsional Moment (STMDE), is on elastostatic analysis of straight FGM beams with rectangular hollow cross-sections. The influence of the variation of the material properties with respect to two or three directions on the angle of twist and the bimoment normal and torsional shear stresses is investigated. The obtained results are compared with the ones calculated by a very fine mesh of standard solid finite elements. This FGM warping non-uniform torsion beam finite element can be used not only in torsional analysis of general thin-walled beams but also in the design of FGM sensors and actuators in mechatronics.

A Mechatronic Brake Booster for Electric Vehicles: Design, Control, and Experiment

The electro-mechanical brake booster (EMBB) is a kind of mechatronic actuator, which is developed to suit the brake assist requirement of electric vehicles. In this paper, we report on the design of an EMBB system consisting of a dc motor, a two-state reduction of a gear and ball screw, a servo body, and a reaction disk. Considering the inconvenience of installation and high price of the pedal force sensor, we translate the control problem of brake power assist control to position tracking control. Meanwhile, a nonlinear control method for position tracking is presented to solve the problem of power assist braking, which is formalized as three parts: the steady-state control, feed-forward control based on reference dynamics, and state-dependent feedback control. The benefit of the nonlinear control method is that it offers a concise control law and performs well in engineering implementations. In addition, a second-order filter was designed to do the signal processing and obtain a higher-order derivative. Finally, the bench tests based on rapid control prototyping environment were designed and implemented to verify the performance of the controller. Test results show that both the position tracking performance and response time of the EMBB system performed well.

Design, Fabrication and Analysis of a Novel Membrane Dielectric Elastomer In-Plane Actuator

The emerging field of soft robots offers the prospective of applying soft actuators as artificial muscles, replacing traditional actuators based on hard materials. Dielectric elastomers (DE), one class of electro-active polymers, represents an attractive technology for the realization of mechatronic actuators, due to their light weight, high energy efficiency and scalability. This work aims at investigating and characterizing a novel design of membrane DE in-plane actuator by magnetic mechanism. A nonlinear dynamic model of the dielectric elastomer actuator (DEA) is established and corresponding material parameters are identified. Natural frequency and response speed of DEAs are studied. It demonstrates that larger stretch and higher response speed can be realized by the proposed DEA.

How nonlinear control can enhance the automobile efficiency and reduce harmful emissions: China case study

China transport energy consumption grows greatly along with dramatically escalated carbon dioxide emissions. Saving energy in transportation is requested for both reducing energy pressure intensity and decreasing relevant emissions. Large scale energy conservation and emission reduction are Chinese automotive industrys’ fundamental objectives. This paper addresses a nonlinear hybrid fuzzy based proportional integral derivative (PID) control methodology to reduce the automobile fuel over-consumption and gases over-emission. After introducing the mathematical model of the automobile Pierburg mechatronic actuator of nonlinear character with parameter uncertainties, its angular displacement is controlled via the proposed PID-fuzzy logic control (FLC) approach. The outputs of the PID controller are the entries of the series-connected FLC. The hybrid topology merges the simplicity and robustness advantages of both the classical PID and the FLC methods respectively. The feedback controller, based on FLC technique, is designed to desirably maintain the angular displacement towards their desired reference values with possible least steady state errors. The proper steady state error elimination will lead to considerable gas emission reduction together with improved energy efficiency. Through Matlab/Simulink tools, the numerical simulations significantly illustrate that the hybrid PID-FLC technique can contribute efficiently in ameliorating the system dynamic behavior in presence of parameter uncertainties. The overall system behavioral analysis enhancement and the proposed controller robustness are experimentally validated.

A finite element model of rigid body structures actuated by dielectric elastomer actuators

This paper presents on finite element (FE) modeling and simulation of dielectric elastomer actuators (DEAs) coupled with articulated structures. DEAs have proven to represent an effective transduction technology for the realization of large deformation, low-power consuming, and fast mechatronic actuators. However, the complex dynamic behavior of the material, characterized by nonlinearities and rate-dependent phenomena, makes it difficult to accurately model and design DEA systems. The problem is further complicated in case the DEA is used to activate articulated structures, which increase both system complexity and implementation effort of numerical simulation models. In this paper, we present a model based tool which allows to effectively implement and simulate complex articulated systems actuated by DEAs. A first prototype of a compact switch actuated by DEA membranes is chosen as reference study to introduce the methodology. The commercially available FE software COMSOL is used for implementing and coupling a physics-based dynamic model of the DEA with the external structure, i.e., the switch. The model is then experimentally calibrated and validated in both quasi-static and dynamic loading conditions. Finally, preliminary results on how to use the simulation tool to optimize the design are presented.

Vibration decrease of electromechanical actuators based on roller screw mechanisms

The reduction of the vibratory activity of the roller screw mechanism (RSM) for converting a rotational movement into a translational movement is discussed. A mathematical model of vibratory activity roller screw mechanisms on the basis of elastic compliances was developed. The resulting equation for calculating the natural frequencies of the basic RSM elements – screw, rollers and nut was obtained. It is proved that the RSM has a low vibroactivity that allows you to create mechatronic actuators, the maximum level of vibration does not exceed 60 to 62 dB, which is 11-16 dB below the level of vibratory activity gear mechanisms.

An Engine/Vehicle Model to Assess the Theoretical Increase of Car Safety by Using the Spark Ignition Engine to Support the Conventional Braking System

Introduction of active safety systems has led to a significant increase of passenger car safety. However, statistics on road accidents show that further improvements of active systems would be necessary. This paper presents a dynamical model of the engine–car–brakes system that is used to simulate vehicle deceleration and calculate the risk of injuries. The model is used to quantify the performance of active safety systems during specific collision scenarios in which several vehicle cruising speeds and different values of distance from the obstacle that causes the active system activation are considered. The base system constituted by actual hydraulic brakes with embedded ABS is first compared to the ideal active system. The latter allows for maximum vehicle deceleration owing to ideal operation of hydraulic brakes supported by ABS and also to mechatronic actuation which anticipates the human intervention and eliminates the delay due to reaction time. Then, the model is used to analyse two feasible evolutions of the ideal active safety system. In the first one, the internal combustion engine friction power aids the vehicle speed decrease before the action of brakes. In the second one, specifically devoted to vehicles powered by hybrid electrical–thermal units, the reversible electric motor operates in addition/substitution to the braking action exerted by the engine mechanical friction.

An Engine/Vehicle Model to Assess the Theoretical Increase of Car Safety by Using the Spark Ignition Engine to Support the Conventional Braking System

Introduction of active safety systems has led to a significant increase of passenger car safety. However, statistics on road accidents show that further improvements of active systems would be necessary. This paper presents a dynamical model of the engine–car–brakes system that is used to simulate vehicle deceleration and calculate the risk of injuries. The model is used to quantify the performance of active safety systems during specific collision scenarios in which several vehicle cruising speeds and different values of distance from the obstacle that causes the active system activation are considered. The base system constituted by actual hydraulic brakes with embedded ABS is first compared to the ideal active system. The latter allows for maximum vehicle deceleration owing to ideal operation of hydraulic brakes supported by ABS and also to mechatronic actuation which anticipates the human intervention and eliminates the delay due to reaction time. Then, the model is used to analyse two feasible evolutions of the ideal active safety system. In the first one, the internal combustion engine friction power aids the vehicle speed decrease before the action of brakes. In the second one, specifically devoted to vehicles powered by hybrid electrical–thermal units, the reversible electric motor operates in addition/substitution to the braking action exerted by the engine mechanical friction.

Motor Selection in Mechatronic Systems Using 2k DoE Method

Mechatronic systems are used as control and drive units in many engineering applications from space technology to robot arms. The main drive units of mechatronic actuator systems are the DC motors. The selection of motor to be used in the systems is an important task in projects. The most suitable motor, which answers the requirements of the project, should be selected. In this article, the studies in the scope of selecting the motor for the mechatronic actuator system of a given capacity are disclosed. Unlike the related studies in literature, in this study Design of Experiment (DoE) method is used. 2k factorial methods have been used as a DoE method. With 2k factorial methods fewer tests conducted according to the full factorial method that uses combinations of all inputs and selection of most suitable motor for the requirements is succeeded.

Central Vehicle Dynamics Control of the Robotic Research Platform RoboMobil

The ROboMObil is DLR’s space-robotics driven by-wire electro-mobile research platform for mechatronic actuators, vehicle dynamics control, human machine interfaces, and autonomous driving (DLR = German Aerospace Center). Due to its four highly integrated identical Wheel Robots it exhibits an extraordinary manoeuvrability even allowing for driving sideward or rotating on the spot. Topics related to vehicle dynamics control are addressed in this article.

Adaptive backstepping output feedback control of DC motor actuator with friction and load uncertainty compensation

SummaryIn this paper, we present an output feedback backstepping controller for mechatronic actuators with dynamic adaptive parameters for friction and load compensation. The targeted application is angular position control of automotive mechatronic valves, which possess nonlinear dynamics due to friction. The proposed controller requires only position measurement. The velocity, current, and friction dynamics are obtained by estimation and observation. The adaptive control law compensates the variations in friction behavior and load torque variation, which are common in real life applications. Lyapunov analysis has been used to show the asymptotic convergence of the closed‐loop system to zero. Simulation and laboratory experimental results illustrate the effectiveness and robustness of the controller. Further experiments on an engine test bench demonstrate the applicability of this controller in commercial engines, as well as its effectiveness as compared with conventional PI controllers.Copyright © 2014 John Wiley & Sons, Ltd.

Overview of the modelling techniques of actuator non-linearities in the engine air path

This paper presents a synthesis of non-linearities present in mechatronic air path actuators of diesel engines. These actuators allow precise control over air path dynamics because of their fast response times and accuracy in transient conditions. However, the non-linearities present in their characteristics limit their closed-loop performance. In this paper we discuss various non-linear phenomena existing in actuator characteristics and their physical causes. Different modelling schemes for the physical causes are also presented, which simulate the non-linear behaviour of the actuators. Furthermore, other factors, such as operational conditions and ageing, and their degrading effects on the actuator performance, are also discussed.

Second-order sliding mode controllers: an experimental comparative study on a mechatronic actuator

Numerous advanced control techniques for actuator control of an engine’s air path have been developed in recent years. Among these approaches, the performance of sliding mode controllers stands out due to their robustness against changes in the physical conditions around the engine. This paper presents the design and testing of three high-order sliding mode controllers and a comparison of their performance in controlling a mechatronic engine air path valve. The most effective strategies are further tested for their robustness against variations in temperature and load conditions. The experimental results show the effectiveness and robustness of the controllers. Comparative results are presented that allow the performance of the considered algorithms to be compared both with respect to each other and with respect to sliding surfaces.