Linear Motor Actuator Research Articles

Active pendulation control of hoisting systems of ship-mounted cranes under ocean wave excitations: Principle and experimental study

Large-scale ship-mounted cranes are important facilities for marine construction. However, under harsh sea conditions, the hoisting system of a ship-mounted crane is often subjected to wave loadings, leading to frequent occurrences of large-amplitude resonance. This paper proposes an active control method, termed the active displacement compensation (ADC) approach, designed for suppressing the large-amplitude pendulation of the hoisting system of ship-mounted cranes. By controlling the position of the suspension point of the hoisting system using linear-motion actuators, the input excitations of the hoisting system induced by the ship motions can be partially or fully compensated in real-time. Therefore, the proposed ADC approach can significantly suppress the large-amplitude pendulation of the hoisting system. The optimal feedback gain and time delay of the ADC approach are theoretically obtained. The ADC approach has been validated by using a six-degree-of-freedoms shaking table test and numerical simulation on the in-plane pendulation suppression of a small-scale hoisting system. Experimental results indicate that the ADC approach achieves a pendulation reduction ratio between 85 % and 89 % for the hoisting system subjected to scaled ship motion records. This study may help develop efficient active control techniques for hoisting systems of ship-mounted cranes under harsh sea conditions.

Electrical Launch Catapult and Landing Decelerator for Fixed-Wing Airborne Wind Energy Systems

This paper presents a (pre)feasibility study of the rail-based ultra-short launch and landing system ElektRail for fixed-wing airborne wind energy systems, such as Ampyx Power. The ElektRail concept promises airborne mass reductions through the elimination of landing gear as well as decreased landing stresses and ground stability requirements, opening possibilities for improved aerodynamics through a single fuselage configuration. Initially designed for operating fixed-wing drones from open fields, the ElektRail concept had to be significantly shortened for application in an airborne wind energy (AWE) context. This shorter size is required due to the much more limited space available at AWE sites, especially on offshore platforms. Hence, a performance enhancement using the integration of a bungee launching and landing system (BLLS) was designed and a system dynamics model for the launch and landing was derived. The results demonstrated the possibility for the ElektRail to be shortened from 140 m to just 19.3 m for use with an optimised tethered aircraft with a mass of 317 kg. A system length below 20 m indicates that an enhanced ElektRail launch and landing concept could be viable for airborne wind energy operations, even with relatively low-tech bungee cord boosters. Linear motor drives with a long stator linear motor actuator could potentially shorten the system length further to just 15 m, as well as provide better control dynamics. An investigation into improved AWE net power outputs due to reduced airborne mass and aerodynamic improvements remains to be conducted.

Force Distribution Within Spinal Tissues During Posterior to Anterior Spinal Manipulative Therapy: A Secondary Analysis.

BackgroundPrevious studies observed that the intervertebral disc experiences the greatest forces during spinal manipulative therapy (SMT) and that the distribution of forces among spinal tissues changes as a function of the SMT parameters. However, contextualized SMT forces, relative to the ones applied to and experienced by the whole functional spinal unit, is needed to understand SMT’s underlying mechanisms.AimTo describe the percentage force distribution between spinal tissues relative to the applied SMT forces and total force experienced by the functional unit.MethodsThis secondary analysis combined data from 35 fresh porcine cadavers exposed to a simulated 300N SMT to the skin overlying the L3/L4 facet joint via servo-controlled linear motor actuator. Vertebral kinematics were tracked optically using indwelling bone pins. The functional spinal unit was then removed and mounted on a parallel robotic platform equipped with a 6-axis load cell. The kinematics of the spine during SMT were replayed by the robotic platform. By using serial dissection, peak and mean forces induced by the simulated SMT experienced by spinal structures in all three axes of motion were recorded. Forces experienced by spinal structures were analyzed descriptively and the resultant force magnitude was calculated.ResultsDuring SMT, the functional spinal unit experienced a median peak resultant force of 36.4N (IQR: 14.1N) and a mean resultant force of 25.4N (IQR: 11.9N). Peak resultant force experienced by the spinal segment corresponded to 12.1% of the total applied SMT force (300N). When the resultant force experienced by the functional spinal unit was considered to be 100%, the supra and interspinous ligaments experienced 0.3% of the peak forces and 0.5% of the mean forces. Facet joints and ligamentum flavum experienced 0.7% of the peak forces and 3% of the mean forces. Intervertebral disc and longitudinal ligaments experienced 99% of the peak and 96.5% of the mean forces.ConclusionIn this animal model, a small percentage of the forces applied during a posterior-to-anterior SMT reached spinal structures in the lumbar spine. Most SMT forces (over 96%) are experienced by the intervertebral disc. This study provides a novel perspective on SMT force distribution within spinal tissues.

Model Predictive Thrust Force Control for Linear Motor Actuator used in Active Suspension

As the core mechanism of active suspension, the control strategy of linear motor actuator is the key factor to affect ride comfort. This paper presents a model predictive thrust force control (MPTFC) method with switching frequency term in the evaluation function for linear motor applied in the vehicle active suspension system. MPTFC selects seven voltage vectors that the inverter produces into the motor predictive model. The motor operating status parameters of the control cycle are obtained with the effect of different voltage vectors. Based on the evaluation function to select the optimal voltage vector, the optimal vector is used for motor in the next control period. The sky-hook controller of active suspension system and the model predictive thrust controller of linear motor are consisted of the control system of the active suspension. A two-degree-of-freedom quarter-car model with active suspension system was established. The MPTFC and the direct thrust force control (DTFC) for linear motor are experimentally tested by dSPACE. The whole active suspension performance is simulated. Results prove that the suspension using linear motor with MPTFC has faster dynamic response of speed, less thrust force and stator flux linkage ripple, which produces the desired electromagnetic force according to the vibration of the bodywork.

Kinematics and control approach for deployable and reconfigurable rigid bar linkage structures

Deployable building structures able to respond to varying environmental and functional conditions through shape transformations aim at an interactive and optimized behaviour towards sustainability of our built environment. A kinematics approach applied to a lightweight linkage structure is presented that builds upon aspects of flexibility and controllability through modularity and simple actuation requirements. The principal planar structure consists of serially connected rigid members. One side of the linkage is pinned to the ground and the other side is pinned to a sliding block. A single linear motion actuator detached from the structural body, acts on the sliding block, while all intermediate joints are equipped with brakes. The reconfiguration approach involves the stepwise selective locking of joints, to define a generic one degree-of-freedom (1-DOF) ‘effective crank–slider’ (ECS) mechanism. The approach is examined through simulation studies followed by hardware implementation on a small scale 1:10 prototype.

A Novel Endocrine Composite Fuzzy Control Strategy of Electromagnetic Hybrid Suspension

To effectively improve the vehicle suspension dynamic performances, minimizing discomfort of passengers and realize vibration energy recovery, a new kind of electromagnetic hybrid suspension (EMHS) system with parallel structure of linear motor and solenoid valve shock absorber is put forward. The linear motor actuator can work at the active state for active control or energy-regenerative state for energy recovery, the solenoid valve shock absorber work at the semi-active state for damping control. Firstly, for the analysis of the hybrid suspension, a quarter dynamic model of EMHS is established. Meanwhile, the mathematical models of linear motor actuator and solenoid valve shock absorber are founded, respectively. Then, for the better suspension control effect based on fuzzy control strategy, a novel endocrine composite fuzzy control strategy is designed. By learning the biological endocrine hormone regulation mechanism, the endocrine control with long feedback and ultra-short feedback is designed. The control laws of the fuzzy controller and endocrine controller are, respectively, designed. Finally, the simulation analysis of suspension dynamic performances and energy-regenerative characteristics is done, respectively. At the same time, the bench test is carried out based on the rapid control prototype with dSPACE platform. The results show the control effect of endocrine composite fuzzy control is better than that of fuzzy control, which improves the dynamic performances. Moreover, part of vibration energy is recovered.

Fuzzy control of the dual-stage feeding system consisting of a piezoelectric actuator and a linear motor for electrical discharge machining

Gap width is an important factor that affects material removal rate, surface finish, and machining stability in electrical discharge machining processes. This research is to develop a novel control method for a new hybrid positioning system which consists of a linear motor and a piezoelectric actuator for high-efficiency electrical discharge machining processes. In the new system, the linear motor provides the macro feeding while the piezoelectric actuator feeds the workpiece in micro scale at high frequency. To reduce the delay caused by separate movements of the linear motor and piezoelectric actuator, a new control algorithm was developed to synchronize the movements of the motor and piezoelectric actuator. A fuzzy control system was used to control the feeding process. Piezoelectric actuator position and its speed were selected as the fuzzy inputs, while the fuzzy output was the linear motor speed. Cutting experiments were conducted, and results show that the fuzzy system is more powerful than the conventional algorithm and the new algorithm with constant motor speed. An increase in material removal rate of 1.6 times was achieved using the proposed fuzzy control algorithm.

A Novel Thrust Force Test Method for a Class of Precision Noncontact Linear Motion Actuators

Precision linear motion is widely used in industrial application. For precision linear motion actuators, ripples of thrust force can deteriorate the driving performance and increase mechanical vibrations. It is very important to precisely test the thrust force of a linear motion actuator. This paper proposes a novel method based on testing reaction force and on the aerostatic method to achieve high-precision and universal testing capability. In this method, the mover and the stator of tested linear motion actuators are suspended by two air-bearing modules. In contrast to traditional testing methods, the force sensor is connected to the stator to avoid the influence of vibration on the sensor. The air-bearing modules eliminate the friction between the stator and the mover, so that it would not affect the results. To validate the strategy, a sample testing platform is manufactured, then a series of experiments is carried out, and the testing performance is compared with that of the traditional method. Experimental results demonstrate the high accuracy achieved by eliminating interferences due to friction and the vibration of the force sensor.

A novel deformable lung phantom with programably variable external and internal correlation.

Lung motion phantoms used to validate radiotherapy motion management strategies have fairly simplistic designs that do not adequately capture complex phenomena observed in human respiration such as external and internal deformation, variable hysteresis and variable correlation between different parts of the thoracic anatomy. These limitations make reliable evaluation of sophisticated motion management techniques quite challenging. In this work, we present the design and implementation of a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers. An in-house-designed lung module, made from natural latex foam was inserted inside the outer shell of a commercially available lung phantom (RSD, Long Beach, CA, USA). Radiopaque markers were placed on the external surface and embedded into the lung module. Two independently programmable high-precision linear motion actuators were used to generate primarily anterior-posterior (AP) and primarily superior-inferior (SI) motion in a reproducible fashion in order to enable (a) variable correlation between the displacement of interior volume and the exterior surface, (b) independent changes in the amplitude of the AP and SI motions, and (c) variable hysteresis. The ability of the phantom to produce complex and variable motion accurately and reproducibly was evaluated by programming the two actuators with mathematical and patient-recorded lung tumor motion traces, and recording the trajectories of various markers using kV fluoroscopy. As an example application, the phantom was used to evaluate the performance of lung motion models constructed from kV fluoroscopy and 4DCT images. The phantom exhibited a high degree of reproducibility and marker motion ranges were reproducible to within 0.5mm. Variable correlation was observed between the displacements of internal-internal and internal-external markers. The SI and AP components of motion of a specific marker had a correlation parameter that varied from -11 to 17. Monitoring a region of interest on the phantom's surface to estimate internal marker motion led to considerably lower uncertainties than when a single point was monitored. We successfully designed and implemented a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers.

Control design for a lower-limb paediatric therapy device using linear motor technology

Abstract Background Rehabilitation robots support delivery of intensive neuromuscular therapy and help patients to improve motor recovery. This paper describes the development and evaluation of control strategies for a novel lower-limb paediatric rehabilitation robot, based on linear-motor actuator technology and the leg-press exercise modality. Methods A functional model was designed and constructed and an overall control strategy was developed to facilitate volitional control of pedal position based on the cognitive task presented to the patient, together with automatic control of pedal forces using force feedback and impedance compensation. Results Each independent drive for the left and right legs can produce force up to 288 N at the user's foot. During dynamic testing, the user maintained a variable target position with root-mean-square tracking error (RMSE) of 3.8 ° with pure force control and 2.8 ° with combined force/impedance control, on a range of periodic motion of 20–80 °. With impedance compensation, accuracy of force tracking was also slightly better (RMSE of 9.3 vs. 9.8 N, force/impedance vs. force control only). Conclusions The control strategy facilitated accurate volitional control of pedal position and, simultaneously, accurate and robust control of pedal forces. Impedance compensation showed performance benefits. Control accuracy and force magnitude are deemed appropriate for rehabilitation of children with neurological impairments, but, due to current levels required, linear motor technology may not be suitable for applications where higher force is needed. Further work is required to validate the device within the target population of impaired children and to develop appropriate patient-interface software.

Study on Active Micro-vibration Isolation System with Linear Motor Actuator

An active micro-vibration isolation control system with linear motor actuators has been proposed and studied. The system is supported by the air springs and symmetrically placed linear motor actuators. A mathematical model of the micro-vibration isolation platform is established, and the optimal control algorithm is designed for isolating vibration system. Simulation and experiment is carried out to verify the effectiveness of active micro-vibration control system. The results demonstrate that the proposed micro-vibration control system has good isolation performance and the linear motor can be used as the active actuator.

Enhanced-Performance Control of an Electromagnetic Solenoid System Using a Digital Controller

Solenoids can be used as linear or incremental motion actuators, most often by coupling the solenoid armature to a linear spring. In this configuration, its limited open-loop stable range (less than one-third of the full range) affects performance and limits applications. The input–output linearization control method is an effective technique to extend the stable range. But in practice, however, the time-delay effect from both measurement and actuation can make the system less damped and therefore more sensitive to disturbances. This effect was analyzed and a digital proportional and integrator controller plus extended state observer (ESO) is proposed to enhance the performance of the electromagnetic actuator. Simulation and experimental tests show that this combined proportional and integral and ESO technique can extend the stable range of motion to 77.6% of full stroke with less sensitivity to external disturbances.

Measurement of the passive stiffness of ankle joint in 3 DOF using stewart platform type ankle foot device.

This paper presents a method to measure the passive stiffness of an ankle joint in three degrees of freedom (DOF) under two motion speeds (1 Hz and 5 degree/s) using a developed Stewart platform-type device. The developed device can reproduce input motions of the foot in 6 DOF by controlling six pneumatic linear motion actuators. We used the device to measure the passive stiffness of an ankle joint undergoing three kinds of motion, namely dorsi-plantar flexion, inversion-eversion, and adduction-abduction. The measured values of the passive stiffness of the ankle joint in dorsiflexion that we obtained agreed well with that obtained in a previous study, indicating that the developed device is useful for measuring the passive stiffness of ankle joint. In addition, the developed device can be used to measure the stiffness in inversion-eversion and adduction-abduction motions as well, parameters that have never been measured. The results we obtained demonstrated certain interesting features as we varied both the direction and pace of motion (e.g., there were significant differences in the stiffness not only between adduction and abduction during the faster pace, but also between these and the other motions).

2P1-B07 リンク機構を用いた上肢作業補助機の改良

The purpose of this study is to develop a lighter and smaller power assist machine that can assist the user's arm to reduce burden on farm workers. The assist machine consists of a mounting part and a linkage mechanism in order to use a single actuator. In this paper, we used a linear motion actuator and a ratchet mechanism. The ratchet mechanism is used to assist the upper limbs without using an actuator. As a result, it is possible to keep the work posture of the upper limbs without controlling an actuator. The effectiveness of the improved power assist machines is verified by the result of the experiments.

Real-time hybrid simulation approach for performance validation of structural active control systems: a linear motor actuator based active mass driver case study

SUMMARY Small-scale models have been commonly utilized in testing of performance of active mass driver (AMD) control systems. The utmost reason is that physical testing of AMD system at full scale is usually too expensive to afford, as well as hard to implement on site. With reference to the real-time hybrid simulation technology, a real-time AMD subsystem testing method is proposed in this paper. In this method, the entire system is composed of AMD as physical subsystem and target structure as numerical subsystem. The physical test is conducted on AMD subsystem, whereas the numerical simulation is carried out on the structure subsystem. Meanwhile, the real-time data are being communicated between these two subsystems. This method is then applied to the performance validation of a novel AMD control system, which is driven by a linear motor. In the test, a benchmark three-storey frame structure is employed as the numerical subsystem, and earthquake excitations are used as the external input. On the basis of a series of tests, both the time history and the statistical criteria show that the results of AMD subsystem and structure subsystem obtained in the real-time AMD subsystem test agree well with the simulation results. Furthermore, all the test results show good repeatability. Therefore, the feasibility and reliability of the proposed real-time AMD subsystem testing approach for performance validation of AMD subsystem has been demonstrated. Such kind of experimental method is efficient in terms of reducing cost associated with performance validation of large-scale active control systems prior to the implementation. Copyright © 2013 John Wiley & Sons, Ltd.

REVIEW ON PIEZOELECTRIC, ULTRASONIC, AND MAGNETOELECTRIC ACTUATORS

Piezoelectric actuators operating in piezoelectric-induced strain/stress or electromechanical resonance-induced vibration or wave-motion friction drive mechanism have shown many advantages over traditional electromagnetic motors, especially, when miniaturizing into millimeter-scale size, while magnetoelectric actuators operating in magnetostrictive mechanism are capable of piezoelectric self-sensing and remote operation under an applied magnetic field. This paper summarizes the recent progresses in piezoelectric ceramic and single crystal materials based actuators and micromotors, ferromagnetic/ferroelectric laminated magnetoelectric actuators, including rotary, linear, planner, and spherical motion actuators, and bending motion magnetoelectric actuators. Their driving mechanisms, operation properties, and applications are also explained.

S053043 静止状態から加速運動を行う円柱の抗力特性と渦構造の関係

Vortex structure and drag characteristic of a circular cylinder accelerated from a rest were investigated by drag measurement and flow visualization techniques. The circular cylinder installed in a linear-motor actuator system moves with a constant acceleration in a water tank. The drag measurement of the circular cylinder was conducted by the measurement equipment using the expansion of coil. The wake flow of a circular cylinder is visualized by using the dye. The formation and the collapse process of the twin vortex and shedding vortices were observed during accelerated motion of the circular cylinder. From the results of flow visualization, the drag was increased after the formation of twin vortex. The drag gradually increased after the collapse of twin vortex. Then the drag increased rapidly after the formation of shedding vortices.

Electromagnetic Field of Resonance Linear Motion Actuator and its Finite Element Analysis which Applied to Coal Mine

In this paper, we have introduced the structure of resonance linear motion actuator which applied to coal mine. And we have built two-dimensional analyzing model by using finite element method. On the basis of the analysis, we have calculated the motor’s air-gap field and magnetism, and we also have studied the affection of motor which caused by permanent magnet’s size. We have studied motor’s winding current when it operates at constant amplitude, and the corresponding experiment results have verified the correctness of finite element model. We have studied the numerical value calculation of resonance linear motion actuator and calculation of its magnetism characteristic. What we have analyzed shows that the air-gap field of motor changes continuously and the magnetism is proportional to winding current. And the results can help technologists to design this kind of motor.

Flows Between the Bottom of Moving Rectangular Body and the Plane Wall

Laminar flows between the bottom surface of a moving rectangular body and the plane wall are investigated experimentally using a towing wind tunnel facility where the model is carried in still air by a linear-motor actuator. The Reynolds number based on the moving speed and the distance between the bottom of the moving body and the fixed plane wall is about 170. In the transient stage of the flow development including the acceleration stage immediately after the body starts to move, the flow is driven not only by viscous shearing stress but also pressure gradient so that the maximum flow velocity exceeds the speed of the moving body. After the flow becomes steady, the normal-to-wall velocity distribution tends to the linear profile of the Couette flow except near the leading edge of the moving body where the flow is still affected by pressure gradient. In addition, the same rectangular-body is carried between two side-walls set normal to the plane wall. For such a nearly two-dimensional configuration, the flow develops to a Couette-Poiseuille flow.

Relation between electrocardiographic repolarization changes and left ventricular filling pressure evaluated by Doppler echocardiography in patients with hypertensive heart disease

Rehabilitation robots support delivery of intensive neuromuscular therapy and help patients to improve motor recovery. This paper describes the development and evaluation of control strategies for a novel lower-limb paediatric rehabilitation robot, based on linear-motor actuator technology and the leg-press exercise modality.A functional model was designed and constructed and an overall control strategy was developed to facilitate volitional control of pedal position based on the cognitive task presented to the patient, together with automatic control of pedal forces using force feedback and impedance compensation.Each independent drive for the left and right legs can produce force up to 288 N at the user's foot. During dynamic testing, the user maintained a variable target position with root-mean-square tracking error (RMSE) of 3.8 ° with pure force control and 2.8 ° with combined force/impedance control, on a range of periodic motion of 20–80 °. With impedance compensation, accuracy of force tracking was also slightly better (RMSE of 9.3 vs. 9.8 N, force/impedance vs. force control only).The control strategy facilitated accurate volitional control of pedal position and, simultaneously, accurate and robust control of pedal forces. Impedance compensation showed performance benefits. Control accuracy and force magnitude are deemed appropriate for rehabilitation of children with neurological impairments, but, due to current levels required, linear motor technology may not be suitable for applications where higher force is needed. Further work is required to validate the device within the target population of impaired children and to develop appropriate patient-interface software.