Actuator Control Research Articles

Introduction of a novel longitudinal-flexural-torsional actuator using a magnetostrictive rod

Abstract This paper presents a novel bulk magnetostrictive actuator, utilizing a rod made of Permendur alloy. This actuator demonstrates versatility in accommodating longitudinal, torsional, and flexural deformations. Longitudinal deformation is induced by applying magnetic fields along the material’s axis, exploiting the Joule effect. The axial magnetic field is generated by a coaxial coil surrounding the material. Torsional deformation is achieved by passing current through the magnetostrictive material and applying circumferential magnetic field, following the Wiedeman effect. To induce flexural deformation, a magnetic field is applied at the material’s surface, facilitated by a magnetic coupler. Actuation is executed using DC magnetic fields, granting the actuator control over four degrees of freedom. Numerical analysis conducted utilizing COMSOL software, showed the combined modes and their mutual influences. The actuator’s displacement range reaches a maximum of 12 µms longitudinally, 7 µms flexurally, and 0.15 degrees torsionally. It also exhibits the capability of simultaneous excitation in two or three different modes. The experiments and studies conducted show the potential application of this innovative actuator in precise positioning systems such as microscopes and optical systems.

Adaptive dynamic programming–based fault-tolerant control of multi-UAV formation system

With the increasing utilization of unmanned aerial vehicle (UAV) swarms in civilian and military field applications, it is crucial to eliminate the potential impacts of UAV faults on task completion and efficiency. To address this issue, the present paper investigates a fault-tolerant control scheme based on the adaptive dynamic programming (ADP) method and fault observer. The whole closed-loop system is composed of a position loop and an attitude loop. An ADP-based position-tracking controller is established with an improved cost function that can simultaneously represent actuator faults, control inputs, and tracking errors. In addition, a single-layer critic neural network is constructed to estimate the cost function and approximate control inputs. In the process of adjusting the weights of the neural network, a unique adjustment method combining policy gradient and prioritized experience replay is adopted to improve the data usage efficiency and speed up the weight convergence. Furthermore, a sliding mode–based attitude controller is utilized for the inner-loop attitude subsystem. The significant feature of this scheme is that it has the ability to self-learn and self-adapt. A Lyapunov stability analysis is performed to verify whether the signals are uniformly ultimately bounded. Finally, simulation experiments are conducted to demonstrate the effectiveness of the proposed scheme.

Neuroadaptive high-order fully-actuated system approach for roll autopilot with unknown uncertainties

In this paper, a neuroadaptive high-order fully-actuated system approach control scheme incorporating the disturbance observer technique is proposed for the missile roll autopilot, subject to model uncertainties generated by the induced roll moment, along with actuator control efficiency deterioration and external disturbance. To address model uncertainties, the radial basis function neural network is implemented. The external disturbance and approximation error are treated as compound disturbances and estimated by a nonlinear disturbance. To avoid the “differential explosion” inherent in the backstepping technique, the high-order fully-actuated system approach is invoked to track the desired roll angle command. The semi-globally uniformly bounded of the closed-loop system is demonstrated via the Lyapunov method. Numerous simulations under various conditions have been conducted to verify the effectiveness of the proposed roll autopilot.

Clamping Force Control of Electromechanical Brake Actuator Considering Contact Point between Friction Lining and Brake Disc

Currently, most electromechanical brake (EMB) schemes are only suitable for passenger cars, and their maximum clamping force is insufficient to satisfy the braking demands of commercial vehicles. Additionally, previous studies on clamping force control are largely based on an EMB equipped with sensors. Due to constraints in installation space and cost, sensorless EMBs are gradually gaining attention. Furthermore, accurately identifying the contact point between the friction lining and the brake disc is the promise of clamping force control for sensorless EMBs. Hence, a sensorless EMB scheme suitable for commercial vehicles is proposed in this study. Secondly, a dynamics model of the EMB actuator is established. After a comprehensive analysis of the proposed EMB actuator, a clamping force control strategy considering the contact points between the friction lining and the brake disc is proposed. Finally, simulation analyses of the strategy are carried out. The results show that the axial length of the proposed EMB actuator is shortened by 17.6% compared with a mainstream pneumatic disc brake. Furthermore, the proposed method can accurately identify the contact points between the friction lining and the brake disc, and the proposed control strategy enables the EMB actuator to achieve the fast response, accurate tracking, and stable maintenance of the target clamping force.

Origami-Inspired Vacuum-Actuated Foldable Actuator Enabled Biomimetic Worm-like Soft Crawling Robot.

The development of a soft crawling robot (SCR) capable of quick folding and recovery has important application value in the field of biomimetic engineering. This article proposes an origami-inspired vacuum-actuated foldable soft crawling robot (OVFSCR), which is composed of entirely soft foldable mirrored origami actuators with a Kresling crease pattern, and possesses capabilities of realizing multimodal locomotion incorporating crawling, climbing, and turning movements. The OVFSCR is characterized by producing periodically foldable and restorable body deformation, and its asymmetric structural design of low front and high rear hexahedral feet creates a friction difference between the two feet and contact surface to enable unidirectional movement. Combining an actuation control sequence with an asymmetrical structural design, the body deformation and feet in contact with ground can be coordinated to realize quick continuous forward crawling locomotion. Furthermore, an efficient dynamic model is developed to characterize the OVFSCR's motion capability. The robot demonstrates multifunctional characteristics, including crawling on a flat surface at an average speed of 11.9 mm/s, climbing a slope of 3°, carrying a certain payload, navigating inside straight and curved round tubes, removing obstacles, and traversing different media. It is revealed that the OVFSCR can imitate contractile deformation and crawling mode exhibited by soft biological worms. Our study contributes to paving avenues for practical applications in adaptive navigation, exploration, and inspection of soft robots in some uncharted territory.

Cooperative Control of Multiple PM Actuators in PMLSM With Segmented Windings

Cooperative Control of Multiple PM Actuators in PMLSM With Segmented Windings

Design and Validation of a Modular, Backdrivable Ankle Exoskeleton.

Partial-assist ankle exoskeletons have been limited by inherent trade-offs between favorable characteristics including high torque capacity, high control bandwidth, back-drivability, compliance, and low mass. Emerging quasi-direct drive actuators have a rigid transmission with a low gear ratio, enabling inherent backdrivability and compliance with accurate torque and position control. Our existing modular, backdrivable exoskeleton system (M-BLUE) uses quasi-direct drive actuators at the hip and/or knee to deliver high assistive torques alongside low dynamic backdrive torques, enabling natural interaction with users with remnant voluntary motion. This paper extends our modular system with the design and validation of a back-drivable ankle exoskeleton module to assist both plantarflexion and dorsiflexion. The bi-directional torque capabilities enable the study of control methods and gait outcomes for able-bodied users and users with gait impairments. Benchtop tests of the actuator performance and control bandwidth indicate that the position, voltage, and current control modes can provide assistance to the ankle joint across activities of daily living (ADLs). We also implement an optimal task-agnostic energy shaping controller for an experiment with a single human subject to validate the ability of the ankle exoskeleton to provide biomimetic torque assistance across a circuit of ADLs.

Thermal Actuator Identification and Control for Thermomechanical Real-Time Cyber–Physical Testing

Thermal Actuator Identification and Control for Thermomechanical Real-Time Cyber–Physical Testing

Closed-loop control of a tendon-driven active needle for tip tracking at desired bending angle for high-dose-rate prostate brachytherapy

Abstract Prostate cancer is the second most common malignancy in American men. High-dose-rate brachytherapy is a popular treatment technique in which a large, localized radiation dose is used to kill cancer. Utilization of curvilinear catheter implantation inside the prostate gland to provide access channels to host the radiation source has shown superiority in terms of improved dosimetric constraints compared to straight needles. To this aim, we have introduced an active needle to curve inside the prostate conformal to the patient’s specific anatomical relationship for improved dose distribution to the prostate and reduced toxicity to the organs at risk. This work presents closed-loop control of our tendon-driven active needle in water medium and air using the position feedback of the tip obtained in real time from an ultrasound (US) or an electromagnetic (EM) tracking sensor, respectively. The active needle consists of a compliant flexure section to realize bending in two directions via actuation of two internal tendons. Tracking errors using US and EM trackers are estimated and compared. Results show that the bending angle of the active needle could be controlled using position feedback of the US or the EM tracking system with a bending angle error of less than 1.00 degree when delay is disregarded. It is concluded that the actuation system and controller, presented in this work, are able to realize a desired bending angle at the active needle tip with reasonable accuracy paving the path for tip tracking and manipulation control evaluations in a prostate brachytherapy.

An electropermanent magnet valve for the onboard control of multi-degree of freedom pneumatic soft robots

To achieve coordinated functions, fluidic soft robots typically rely on multiple input lines for the independent inflation and deflation of each actuator. Fluidic actuators are controlled by rigid electronic pneumatic valves, restricting the mobility and compliance of the soft robot. Recent developments in soft valve designs have shown the potential to achieve a more integrated robotic system, but are limited by high energy consumption and slow response time. In this work, we present an electropermanent magnet (EPM) valve for electronic control of pneumatic soft actuators that is activated through microsecond electronic pulses. The valve incorporates a thin channel made from thermoplastic films. The proposed valve (3 × 3 × 0.8 cm, 2.9 g) can block pressure up to 146 kPa and negative pressures up to –100 kPa with a response time of less than 1 s. Using the EPM valves, we demonstrate the ability to switch between multiple operation sequences in real time through the control of a six-DoF robot capable of grasping and hopping with a single pressure input. Our proposed onboard control strategy simplifies the operation of multi-pressure systems, enabling the development of dynamically programmable soft fluid-driven robots that are versatile in responding to different tasks.

Fuzzy Control of Induction Motor Actuator with Open Loop PID Controller in Water Treatment Plant

يعد التحكم الذكي أداة قوية للغاية للتغلب على جميع الصعوبات في أزمة محطة المياه حيث تم استخدام وحدة سيطرة ضبابية مع المسيطر التناسبي التكاملي التفاضلي للاستفادة من قدرات الضبط التلقائي للسيطرة على المحرك في دائرة محطة الطاقة في هذا العمل استخدمت وحدة سيطرة على المحول الترددي مع المحرك الحثي كمشغل لتثبيت تدفق المياه عبر مسافة محددة مسبقًا. تم استخدام Simscape/Matlab 2020a لمحاكاة دائرة محطة المياه مع محطة الخزان في نظام إمداد المياه قبل اختبارها على مسافات مختلفة لقياس التيار والسرعة وعزم الدوران والجهد. كذلك تم استخدام أربع مضخات وتم تقدير الضغوط على مسافات مختلفة )40 م، 45 م، 60 م( من محطة معالجة المياه مع وحدة السيطرة المنطقية الضبابية ذات قواعد 7x7 مع محرك الاستدلال من نوع Mamdani. اظهرت النتائج لهذا العمل قدرة كبيرة على ثبات المعلمات الكهربائية، ثبات الضغط وبالنتيجة استقرار النظام المقترح.

Adaptive sliding-mode delay compensation for real-time hybrid simulations with multiple actuators

Real-time hybrid simulation (RTHS) is a widely applied test method in structural engineering, which is developed from pseudo-dynamic test. Much of the past work has been centered on one-dimensional RTHS using a single hydraulic actuator. When the complexity of the problem demands to increase the number of degrees of freedom to be enforced on the boundary conditions, more than one hydraulic actuator must be used. Multiple-actuator or multi-axial RTHS (maRTHS) requires that more than one hydraulic actuator exerts the required motion on experimental substructures demanding the implementation of multiple-input multiple-output (MIMO) control strategies. A new maRTHS benchmark control problem has been developed, focusing on a frame subjected to seismic load at the base, substantially transforming and intensifying the complexity of the problem. The time delay generated by the dynamic characteristics of the loading system and the transmission process as well as the high coupling between the hydraulic actuators and the nonlinear kinematics escalates the complexity of the actuator control tracking. A sliding mode adaptive delay compensation method suitable for maRTHS is proposed, which utilizes a MIMO sliding mode method to reduce the coupling effects of actuators and the adaptive compensation method to compensate the residual delay. The effectiveness of the method is verified by numerical simulating different working conditions in the Benchmark Problem Platform.

Study on Chassis Leveling Control of a Three-Wheeled Agricultural Robot

Three-wheeled agricultural robots possess the advantages of high flexibility, strong maneuverability, and low cost. They can adapt to various complex terrains and operational environments, making them highly valuable in the fields of crop planting, harvesting, irrigation, and more. However, the horizontal stability of the three-wheeled agricultural robot chassis is compromised when working in harsh terrain, significantly impacting the overall operational quality and safety. To address this issue, this study designed a leveling system based on active suspension and proposed a stepwise leveling method based on an adaptive dual-loop composite control strategy (ADLCCS-SLM). Firstly, in the overall control of the three-wheeled chassis, a stepwise leveling method (SLM) was introduced. This method allows for rapid leveling by incrementally adjusting one or two suspensions, effectively avoiding the complex interactions between suspension components encountered in traditional methods involving the simultaneous linkage of three suspensions. Next, in terms of suspension actuator control, an adaptive dual-loop composite control strategy (ADLCCS) was proposed. This strategy employs a dual-loop composite control both internally and externally and utilizes an improved adaptive genetic algorithm to adjust critical control parameters. This adaptation optimizes the chassis leveling performance across various road conditions. Finally, the effectiveness of the proposed ADLCCS-SLM was validated through simulation and experimental testing. The test results showed that the control effect of the proposed method was significant. Compared to the traditional multi-suspension linkage leveling method based on PID, the peak values of pitch angle and roll angle were reduced by 31.8% and 33.3%, respectively.

[formula omitted]adaptive resonance ratio control for series elastic actuator with guaranteed transient performance

Series elastic actuator (SEA) technology is promising for the development of compliant robotic joints. Despite advancements in the realization of precise tracking, challenges persist in controlling the vibration and transient performance. This study enhanced the resonance ratio control (RRC) algorithm by integrating it with the L1 adaptive control (L1AC) method to address overshoot, static error, and vibration in SEA position control. Initially, the resonance between the motor and link sides caused by the elastic transmission structure was analyzed, which can result in overshoots and vibrations that affect the transient performance of the SEA control. Subsequently, a control scheme based on L1AC was introduced to enhance the performance. The stability of the proposed algorithm was demonstrated through a comprehensive exploration of key control parameters. Furthermore, the algorithm was augmented with gravity compensation, effectively reducing the predicted and reference errors. Consequently, the transient performance was improved. The efficacy of this enhanced algorithm was validated through simulations and experimental platforms, and comparisons with the RRC and model reference adaptive control algorithms. In all the experiments, the overshoot did not exceed 1.1%, the maximum jitter amplitude on the link side was within 0.2° , and a larger time constant in the controller could effectively eliminate the overshoot and vibration with a small response time delay. Furthermore, the algorithm exhibited a protective response during link side collisions by moderating link velocity and limiting motor current, to safeguard the contact environment, humans, and the SEA itself, which take advantage of the L1AC’s low-pass filter (LPF) properties in disturbance handling.

A comparative analysis between deep neural network-based 1D-CNN and LSTM models to harness the self-sensing property of the shape memory alloy wire actuator for position estimation

The article presents a performance-based comparative analysis of popular deep neural network (DNN) models such as 1-dimensional convolutional neural network (1D-CNN) and long short-term memory (LSTM) for position estimation of shape memory alloy (SMA)-based wire actuator. These DNN models utilize the self-sensing property (SSP) for position estimation of the SMA actuator. The phase-dependent electrical resistivity of SMA wire acts as SSP, where the electrical resistivity in the form of SMA wire resistance acts as inputs to the proposed models for precise estimation of the current position of the SMA actuator. For effective position control of the SMA actuator, accurate position sensor feedback is required, utilizing SSP results in the elimination of this external sensor. This will improve the overall system in terms of compactness and reduced interface complexity. Coming to DNN models, 1D-CNN has been meagerly explored in the current literature landscape for self-sensing estimation of SMA actuators. These 1D-CNN models are becoming quite popular for time series prediction for various applications and are emerging as an alternative to widely used LSTM models. In this paper, a novel implementation of a 1D-CNN model for SMA actuator position estimation has been done. A comparative analysis between 1D-CNN and LSTM has been done for prediction capability and inference speed based on performance measures such as Mean Square Error (MSE), Mean Absolute Error (MAE), symmetric Mean Absolute Percentage Error (sMAPE), data distribution, and average inference speed. The proposed comparative results show that 1D-CNN has a matching performance with the LSTM model with respect to prediction capability, however, 1D-CNN offers faster inference speed. The analysis of the proposed work can be useful for choosing a suitable DNN model for deployment on low computing platforms such as microcontrollers for SMA actuator-based real-time applications where time latency is a critical parameter.

Research on DSP-based data model identification and triple-loop PID control of electro-hydraulic actuators

This paper focuses on the electro-hydraulic actuator of a certain type of aircraft, detailing the DSP-based hardware structure and principles. The study utilizes data acquisition and data model identification to establish a second-order model for the electro-hydraulic actuator. Verification sets and mean squared error (MSE) calculations, with an MSE value of 0.0110, indicate a reasonable identification model. Subsequently, a controller design structure is proposed based on the identified model. Finally, simulations validate the identified model and the triple-loop PID control. Experimental results show that the system's sine response output amplification factor is 0.9242.

Temperature gradient for improving the output non-linearity in shape memory alloy actuators

The non-linearity of shape memory alloy’s (SMA) input vs. output relationship has been a significant barrier to their broader application for actuators. In this article, we introduce a novel activation approach with the objective of improving the output nonlinearity in SMA actuators by using a liquid temperature gradient for activation. This gradient, with a narrow inflection point, selectively activates and deactivates different portions of the SMA, allowing control of the overall actuator’s output by adjusting the inflection point’s position. Two prototypes with the proposed concept were constructed and tested for force and displacement output. Their inner shape design facilitates the creation of a temperature gradient, whose inflection point is adjusted by varying the mix ratio of the inlet of hot and cold water. The performance of the prototypes was evaluated, including their ability to generate a temperature gradient, output linearity, activation dead time and time constant, and compatibility with a linear controller. The output linearity, activation dead time, and time constant were also compared with traditional wet activation. Our findings suggest that this technique significantly enhances the performance and predictability of SMA-based actuators and is compatible with PID controllers without additional feedforward or modeling techniques, offering a practical solution to a long-standing challenge in the field.

Design and Fabrication of an Autonomous Rice Transplanter

The goal of this study was to create a prototype of an automatically guided rice transplanter using a Pixhauk flight controller, 3DR telemetry, Raspberry Pi, Tof sensor, gyro sensor, and other GPS navigation sensors to determine the field performance of that machine. GPS was used to obtain data such as location, direction, and speed, whereas machine vision can provide a navigation line. The next position of the transplanter can be determined using feature points extracted from the navigation line. The controller area network bus complies with the actuator control command and data communication protocols. Electrical actuators control steering and transmission based on a vehicle's location in a field. The percentage of missing, buried, and floating hills was observed to be 1.6%, 1.4%, and 3.0%, respectively, as the maximum values were found in clay soil at T1. Over time, percentages of losses decreased, and the lowest percentage of losses was given. The lowest percentage of missing, buried, and floating hills was found at 0.8%, 0.2%, and 0.8%, respectively, in clay loam soil at T5. Planting efficiency improved, and losses decreased as treatment levels upgraded. Clay loam soil in T5 had the highest planting efficiency percentage (88%), whereas clay soil in T1 had the lowest (61%) proportion. The findings indicated that T4 and T5 enhanced rice output by decreasing the losses incurred during seedling transplantation. The study suggested that the developed rice transplanter might be suitable for planting rice seedlings to establish meaningful mechanization through precision agriculture technology.

A single-coil-driven tristable electromagnetic mini valve with multiple working states

Electromagnetic mini valves have attracted great interest in medical devices for their excellent performance and high integration. In state-of-the-art research, most mini valves have only two working states, while certain ones featuring three to four working states necessitate multiple driving sources. To solve these problems, a novel tristable electromagnetic mini valve with three stable working states achieved by a single coil was proposed. The actuation mechanism of this mini valve mainly comprises a cylindrical magnet (CM) and a ring magnet (RM) coaxially arranged. In the absence of current through the coil, the stability of the magnets is upheld by their mutual repulsion and the attraction of the iron core. Upon modifying both the magnitude and orientation of the current, one of the magnets traverses from one terminus to another each time. The two magnets are either stationary at the start point or the endpoint. Thereby, four position relationships are formed, three of which are stable. The minimum response time and energy consumption are 3.75 ms and 0.013 J, respectively. The working pressure of the valve ranges from 0 to 200 kPa. The maximum flow rate and back pressure reach 10.5 L/min and 180 kPa, respectively. A tristable design contributes to lower energy consumption, and the three-working-state function actuated by a single coil facilitates a diminution in the size of the mini valve. Consequently, a diminished quantity of valves is realized for multiple degree-of-freedom pneumatic actuator control, which promotes the miniaturization of the whole system. The dimensions and performance of the proposed mini valve substantiate its potential in pneumatic medical devices.

Design, Manufacture and Control of a Multi-layer Piezoelectric Actuator

Design, Manufacture and Control of a Multi-layer Piezoelectric Actuator