翘板式射频MEMS开关的研究

提出了一种新型的翘板式静电射频微系统开关,给出了理论模拟,结构分析结果和工艺制作方法。该结构采用了5μm厚的无应力单晶硅作为开关的可动部分,可以缓解薄膜应力变形。翘板式结构解决了传统静电设计中动作力弱的问题,并且通过调整支点解决了开关回复力不可调的难题。利用该结构可以在保持高隔离度的同时使驱动电压降低,有限元理论模拟驱动电压为5~10V;采用翘板式结构增加了开关的使用周期,而且结构自身具有单刀双掷特点,可以直接应用于高频通信的频道选择。给出了开关共面波导传输线的测试结果和设计讨论。     

Longitudinal wheel slip control using dynamic neural networks

The control of automotive braking systems performance and a wheel slip is a challenging problem due to nonlinear dynamics of a braking process and a tire–road interaction. When the wheel slip is not between the optimal limits during braking, the desired tire–road friction force cannot be achieved, which influences braking distance, the loss in steerability and maneuverability of the vehicle. In this paper, the new approach, based on dynamic neural networks, has been employed for improving of the longitudinal wheel slip control. This approach is based on dynamic adaptation of the brake actuation pressure, during a braking cycle, according to the identified maximum adhesion coefficient between the wheel and road. The brake actuated pressure was adjusted on the level which provides the optimal longitudinal wheel slip versus the brake actuated pressure selected by a driver, the current vehicle speed, load conditions, the brake interface temperature and the current value of the wheel slip. The dynamic neural network has been used for modeling of a nonlinear functional relationship between the brake actuation pressure and the longitudinal wheel slip during a braking cycle. It provided preconditions for control of the brake actuation pressure based on the wheel slip change.     

Design and energetic characterization of a liquid-propellant-powered actuator for self-powered robots

This paper describes the design of a power supply and actuation system appropriate for position or force controlled human-scale robots. The proposed approach utilizes a liquid monopropellant to generate hot gas, which is utilized to power a pneumatic-type actuation system. A prototype of the actuation system is described, and closed-loop tracking data are shown, which demonstrate good motion control. Experiments to characterize the energetic performance of a six-degree-of-freedom actuation system indicate that the proposed system with a diluted propellant offers an energetic figure of merit five times greater than battery-powered DC motors. Projections based on these experiments indicate that the same system powered by undiluted propellant would offer an energetic figure of merit in an order of magnitude greater than a comparable battery-powered DC motor actuated system.     

Contact physics of gold microcontacts for MEMS switches

This work presents a study of gold metallic contacts regarding contact resistance, heat dissipation, and surface damage in the normal-force regime of tens to hundreds of μN, which is typical of the contact forces from microactuation. The purpose of this work is to present the micromechanical switch designer with practical information on gold contact phenomena in this force regime, as most work in micrometallic contacts has focused on contact forces greater than 1 mN. Results indicate actuation forces of several hundred μN are required for reliable fully metallic contacts, with resistance and current carrying ability primarily dependent on morphology, thermal management, and nm-depth material properties of the contact electrodes     

静电梳齿驱动器薄膜变形反射镜

提出一种大冲程静电梳齿驱动器微机械薄膜变形反射镜,理论上研究了静电梳齿驱动器微机械薄膜变形反射镜的静电驱动力和变形位移与驱动电压的关系,分析了变形反射镜的驱动稳定性,比较了平板电容驱动器与纵向梳齿驱动器的驱动能力.结果表明,变形反射镜的静电驱动力和变形位移没有关系;在相同的面积下,纵向梳齿驱动器的驱动力比平板电容驱动器的驱动力大很多.     

Nanometer positioning of a linear motion stage under static loads

A standard lead-screw-driven linear translation table was fitted with a secondary voice coil actuator, which can apply forces of ±0.5 N on the translating stage. The DC servomotor-driven lead screw is capable of positioning the table to a nominal precision of ±0.5 μm. The secondary actuator then positions the table to ±1 mm. Both actuators utilize closed-loop feedback algorithms. This configuration has significant advantages over the more common “piggyback” arrangement, which often uses piezoelectric actuators. The advantages include preservation of the original load surface and position sensors and an easier to control actuator. Its ability to operate under static load and a model of the microdynamic behavior are addressed in this paper. When static loads of up to 36 N were applied to the translating stage, the secondary actuator could still displace the table to ±500 nm and control the position down to its zero-load precision. The microdynamic behavior in this region is nonlinear and was modeled using the modified Dahl model of friction. The key parameters in the model were identified using a 2 Hz sinusoidal input force with varying amplitudes from the secondary actuator. For a constant loading force, the parameters did not vary significantly with different excitation forces. The friction parameter relating the initial slope of the friction force versus displacement curve did change with different loading forces. Also, for smaller input signals causing displacements of less than 200 nm, the friction parameters would tend to drift, depending on input magnitudes     

Dynamic force simulator for multifinger force display

In this paper, the authors present a dynamic force simulator (DFS) for force feedback in human-machine systems. They propose a virtual world model with two force flows: one is the force flow from human to an object, the other is the force flow from an object to human. To use this model, the DFS simulates object dynamics, contact models, and friction characteristics of the human hand interacting with the object in virtual reality. After the derivation of kinematic and force relations between hand and object space, they balance the two forces: one from the human and the other from the object in the contact force space in virtual world and then realize the adequate feedback forces to human operator. Interaction with the DFS allows calculation and feedback of appropriate forces to the force controlled actuators of the sensor glove they have developed. In this paper grasping of a cylinder in the virtual world is presented. During object grasping, they measure joint angles and torques using the sensor glove system. In the future, they will use this system to analyze human dextrous manipulations called human skill     

A new preload mechanism for a high-speed piezoelectric stack nanopositioner

Piezoelectric stack actuators are the actuator of choice for many ultra-high precision systems owning to its fast responses and high pushing force capabilities. These actuators are constructed by bonding multiple piezoelectric layers together. An inevitable drawback of these actuators is that there are highly intolerant to tensile and shear forces. During high-speed operations, inertial forces due to effective mass of the system cause the actuators to experience excessive tensile forces. To avoid damage to the actuators, preload must be applied to compensate for these forces. In many nanopositioning systems, flexures are used to provide preload to the piezoelectric stack actuators. However, for high-speed systems with stiff flexures, displacing the flexures and sliding the actuators in place to preload them is a difficult task. One may reduce the stiffness of the flexures to make the preload process more feasible; however, this reduces the mechanical bandwidth of the system. This paper presents a novel preload mechanism that tackles the limitations mentioned above. The preload stage, which is connected in parallel mechanically to a high-speed vertical nanopositioner, allows the piezoelectric stack actuator to be installed and preloaded easily without significantly trading of the stiffness and speed of the nanopositioning system. The proposed vertical nanopositioner has a travel range of 10.6 μ m. Its first resonant mode appears at about 24 kHz along the actuation direction.     

Control of interaction force in constant-height contact mode atomic force microscopy

Contact mode is a versatile and widely used technique for imaging samples using the Atomic Force Microscope (AFM). When contact mode imaging is performed in constant-height mode, it enables linear and faster response but leads to uncontrolled tip-sample forces. Here, a control strategy based on magnetic actuation is proposed to achieve high-bandwidth control of the tip-sample forces in constant-height contact mode AFM. A magnetic particle attached to the AFM probe is actuated by an external solenoid and employed for force regulation. A quasi-static model has been proposed and employed to develop the control strategy. Likewise, the contact natural-frequency, which decides the limit of achievable speed, has been shown to be significantly higher relative to the free probe and to be relatively insensitive to the particle size. Subsequently, a setup is developed to validate the control strategy and demonstrate reduction of tip-sample force variation by over a factor of 12 compared to conventional constant-height mode operation. Likewise, in comparison with conventional contact mode AFM, an improvement of linearity by over a factor of 9 and improvement in response speed by a factor of 100 have been demonstrated while imaging hard samples. The system has been shown to image topography at speeds of 2.44 frames per second while regulating the interaction force. Finally, the stiffness of a sample has also been characterized using the developed system and simultaneous estimation of topography has also been demonstrated. They are shown to agree well with theoretical expectations.     

An original mechatronic design of a kinaesthetic hand exoskeleton for virtual reality-based applications

Within the new industrial era, the interaction between humans and virtual reality is spreading across our lives. The development of exoskeleton designed to enhance the immersivity of virtual reality environments has a potentially considerable social impact and arises as a hot research topic. The presented work dwells well with the subject by describing the mechatronic design process of a kinaesthetic hand exoskeleton system meant to reproduce proprioceptive stimuli coming from the interaction with a virtual reality. The presented prototype is a modular device, equipped with force and pose sensors, and driven by a Bowden-cable-based remote actuation system. Unlike similar devices, the proposed exoskeleton is specifically thought for VR interaction and is designed to be reversible while exerting up to 15 N per finger. For a more accurate rendering of kinetostatic finger stimuli, a procedure for reconstructing HMI force as a function of measured force and position signals by employing a system’s kinematic and dynamic model is presented, detailed, and followed by some preliminary tests. The results showed that the model can trace forces back to the end-effector with a percentage error below 15%.     

复合自组装分子膜的摩擦特性研究

本文采用自组装技术制备了三氯十八硅烷(octadecyltrichorosilane 0TS)／3-胺基丙基-三甲氧基硅炕(3-amino-propyltrimethoxysilane APTMS)和APTMS／OTS复合自组装分子膜,在原子力／摩擦力显微镜上对薄膜的摩擦特性进行了测试,并与0TS和APTMS自组装分子膜(self-assembledmonolayers SAMs)进行了对比。结果表明,OTS／APTMS复合自组装分子膜因既保持了一定的键合强度叉增加了自组装分子的流动性,使其摩擦力显著降低。复合自组装分子膜的摩擦力随着载荷和滑动速度的增大而增大,这与自组装分子的受力响应和弛豫特性相关。合理地设计自组装分子膜可有效地减小摩擦。     

Networked telemicromanipulation systems "Haptic Loupe"

In this paper, "Haptic Loupe" telemicromanipulation systems are proposed. We have developed telemicromanipulation systems that enable human operators to perform micro tasks, such as assembly or manufacturing without stress . These systems are based on a scaled bilateral teleoperation system between different structures. The systems are composed of an original six-degrees-of-freedom (6-DOF) parallel link manipulator to carry out micromanipulation and a 6-DOF haptic interface with force feedback. A parallel mechanism is adopted as a slave micromanipulator because of its good features of accuracy and stiffness. The haptic master interface is developed for micromanipulation systems. Haptic device system modeling and a model reference adaptive controller are implemented to compensate for friction forces, which spoil the free motion performance and force response isotropy of the system. Total system performance as a telemicromanipulator system is evaluated by performing some primitive manipulation tasks in a teleoperation experiment. Experimental results are presented and discussed.     

Load sensing bearing based road-tyre friction estimation considering combined tyre slip

This work discusses a road-tyre friction estimator considering combined tyre slip. The friction estimator design is motivated by its importance in vehicle dynamics control as accurate friction estimation can improve performance and safety. The estimator uses tyre force measurements from Load Sensing Bearing (LSB) technology and does not rely on parameterized tyre model. The tyre force measurements benefit the estimator mainly because of the uncertainties and nonlinearities of the tyre force characteristics. The proposed estimator uses tyre slip and tyre force representations where the longitudinal and lateral tyre slips and forces are combined into a single tyre slip and tyre force values. This representation makes the method effective during pure longitudinal dynamics, pure lateral dynamics and for combined slip. In addition, individual tyre-road friction estimation is possible with the proposed estimator and a computationally inexpensive algorithm, suitable for real-time implementation, is used to estimate the friction. The estimator is studied in simulation during pure braking, pure cornering and for combined slip. Further, the estimator is simulated in closed loop with a yaw rate controller to study whether the estimator improves vehicle safety. Finally the estimator is validated using test data from several maneuvers performed on a test vehicle instrumented with LSB technology.     

Design of a robust force controller for the new mini motion package using quantitative feedback theory

The use of hydraulic systems in industrial applications has become widespread due to their efficiency advantages. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Mini motion package (MMP) is one type of the new low cost hybrid actuator. This MMP is considered as a novel linear actuator with various applications such as robotics, automation, plastic injection-molding and metal forming technology. However, this efficiency gain is often accompanied by a degradation of system stability and control problems. In this paper, to maintain robust performance requirement, tracking performance specification, and disturbance attenuation requirement, the design of a robust force controller for the new hybrid actuator using quantitative feedback theory (QFT) is presented. A family of plants model for MMP is obtained from experimental frequency responses of the system in the presence of significant uncertainty. Experimental results show that highly robust force tracking by the MMP actuator could be achieved even if the stiffness of environment and set-point force change. In addition, it is understood that the new system has energy-saving effect even though it has almost the same response as that of valve controlled system.     

Theoretical and experimental study of the forces between different SNOM probes and chemically treated AFM cantilevers

A shear-force mechanism between a chemically etched scanning near-field optical microscope tip and different chemically treated atomic force microscope cantilevers has been experimentally and theoretically investigated as a function of the tip-to-sample distance for different amplitudes of the tip oscillation. The experimental results show, in agreement with the theoretical predictions, that as the tip approaches the cantilever, the electrostatic force is the most influential in the shear-force mechanism, independently of the nature of the tip or the sample. As the tip-to-sample distance decreases, other forces come into play, and the type of interaction depends on the chemical nature of tip and sample surfaces. Thus, for hydrophobic cantilevers, the decrease in the vibration amplitude is mostly due to the solid friction forces resulting from electrostatic interactions. However, if the sample surface is hydrophilic, there is a decrease in the electrostatic force, a water meniscus is formed, and the decrease in the tip amplitude is mostly due to dynamic friction related to capillarity.     

Biocompatible Electromechanical Actuators Composed of Silk‐Conducting Polymer Composites

Single‐component, metal‐free, biocompatible, electromechanical actuator devices are fabricated using a composite material composed of silk fibroin and poly(pyrrole) (PPy). Chemical modification techniques are developed to produce free‐standing films with a bilayer‐type structure, with unmodified silk on one side and an interpenetrating network (IPN) of silk and PPy on the other. The IPN formed between the silk and PPy prohibits delamination, resulting in a durable and fully biocompatible device. The electrochemical stability of these materials is investigated through cyclic voltammetry, and redox sensitivity to the presence of different anions is noted. Free‐end bending actuation performance and force generation within silk‐PPy composite films during oxidation and reduction in a biologically relevant environment are investigated in detail. These silk–PPy composites are stable to repeated actuation, and are able to generate forces comparable with natural muscle (>0.1 MPa), making them ideal candidates for interfacing with biological tissues.     

On the investigation of a reliable actuation control method for ohmic RF MEMS switches

Efficient control of RF MEMS switches is a very important issue as it is correlated to main failure mechanisms/modes such as the impact force and bouncing phenomena, which degrade their dynamic performance and longevity. This paper presents the control of specific ohmic RF MEMS switches under three different actuation modes, a tailored pulse optimization method based on Taguchi's technique (voltage mode actuation control), resistive damping (charge mode actuation control) and finally the Hybrid actuation mode, which is a combination of the tailored pulse, the resistive damping and Taguchi's optimization technique. Coventorware simulations indicate that under optimized Tailored pulse and Hybrid actuation modes, the impact velocity is reduced by around 90%, the initial impact force by around 75% and the maximum bouncing displacement during the release phase by around 95%, while the switching speed is increased by around 20% compared with the step pulse control mode. The resistive damping control mode is inappropriate for this type of switch and only partial improvement during the pull-down phase has been achieved. Finally, a comparison between Hybrid and optimized tailored modes shows that Hybrid actuation mode excels with better switching characteristics and most importantly offers immunity to manufacturing and operation tolerances.     

A sensorless torque control for Antagonistic Driven Compliant Joints

Antagonistic Driven Compliant Joints (ADCJs) are object of great interest in current robotics research, representing one of the most widely applied solutions to develop human-like and safe joints for human-robot interaction. Providing the joint with “actively” adjustable hardware compliance, ADCJs have two distinctive features: (1) the joint is powered by two independent “actuation units” and (2) each actuation unit works as a non-linear elastic element with an adjustable resting position. This paper proposes a sensorless torque control strategy suitable for ADCJs actuated robots. This method is based on two steps: (1) off-line characterization of the elasticity of the actuation units, defined by the force–elongation curve and (2) online estimation of the force exerted by each actuation unit, through a direct measure of the joint angle, and of the “resting position” of each actuation unit. The proposed force estimation method can be used to develop two independent force controllers, which can be then combined to regulate the resulting joint torque, with no need of additional torque sensors. The performance of the proposed torque control was evaluated over the shoulder and the elbow ADCJs of the 2-link 2-DOFs planar robotic arm NEURARM. The method proved to work effectively, achieving good performances on the test platform, and represents a suitable alternative to state-of-the-art sensor-based torque controls.     

Comparison of MRI-Compatible Mechatronic Systems With Hydrodynamic and Pneumatic Actuation

The strong magnetic fields and limited space make it challenging to design the actuation for mechatronic systems intended to work in MRI environments. Hydraulic and pneumatic actuators can be made MRI-compatible and are promising solutions to drive robotic devices inside MRI environments. In this paper, two comparable haptic interface devices, one with hydrodynamic and another with pneumatic actuation, were developed to control one-degree-of-freedom translational movements of a user performing functional MRI (fMRI) tasks. The cylinders were made of MRI-compatible materials. Pressure sensors and control valves were placed far away from the end-effector in the scanner, connected via long transmission lines. It has been demonstrated that both manipulandum systems were MRI-compatible and yielded no artifacts to fMRI images in a 3-T scanner. Position and impedance controllers achieved passive as well as active subject movements. With the hydrodynamic system we have achieved smoother movements, higher position control accuracy, and improved robustness against force disturbances than with the pneumatic system. In contrast, the pneumatic system was back-drivable, showed faster dynamics with relatively low pressure, and allowed force control. Furthermore, it is easier to maintain and does not cause hygienic problems after leakages. In general, pneumatic actuation is more favorable for fast or force-controlled MRI-compatible applications, whereas hydrodynamic actuation is recommended for applications that require higher position accuracy, or slow and smooth movements.