Design and analysis of a pneumatic high-impact force drive mechanism for in-pipe inspection robots

A pneumatic actuator is suitable and safe for in-pipe inspection robots in inflammable circumstances because of its ability to withstand explosions. However, ordinary pneumatic actuators limit driving speed because of their slow response. In this paper, we propose a novel pneumatic drive mechanism that can produce a high-impact force to move the in-pipe robot forward with sufficient speed by a catastrophic phenomenon using rapid release between a magnet and springs. We also introduce an anisotropic friction mechanism that uses a self-locking phenomenon to transmit the impact force to the pipe walls efficiently. A pin retraction mechanism that releases the self-locking condition is applied to retrieve the robot from the pipes. Optimizations of the proposed design were conducted based on a motion simulation model and verified in experiments. The experimental results obtained for maximum driving speeds in a straight pipe with different material types were approximately 90 and 50 mm/s for horizontal and vertical pipes, respectively. Stable strokes were also observed at different driving frequencies from 0.5 to 2.0 Hz.     

Analytical behavior of rectangular electrostatic torsion actuators with nonlinear spring bending

In this paper, we study the pull-in effect for rectangular electrostatic torsion actuators by using analytical calculations that include the higher order effects of nonlinear spring bending. The calculation approach speeds the design of such systems. The method is found to be suitable for actuators with single long beam springs where the ratio of the resonant frequencies for the torsion and bending modes is up to at least 3.5, in the region where bending dominates torsion. After fitting the theory in this paper to Coventor simulation results with three nonphysical coefficients, the fractional differences between Coventor simulation and analytical calculation results are smaller than 6%. The method is also suitable for at least one class of folded spring designs, with greatly decreased bending mode displacement. The main results are also verified by comparing them with published experimental results.     

Modeling and resonance suppression control for electro-hydrostatic actuator as a two-mass resonant system

Electro-hydrostatic actuators (EHAs) possess excellent power/weight ratio and space-saving properties. However, uncertainty exists with respect to the presence of non-linear behaviors and dynamic characteristics. Servo pumps, hydraulic motors, and oil-filled pipes can be regarded as motors, loads, and springs, respectively. Hence, EHAs can be modeled as two-mass resonant systems. In this paper, we show a parameter identification method for modeling EHAs as two-mass resonant systems. Then, in order to suppress the effect of resonance, self-resonance cancellation technique is implemented. As a result, phase delay is significantly improved in the position tracking.     

Development of a control system for an omni-directional vehicle with step-climbing ability

This paper proposes a control method for wheels to pass over rough terrain. In our previous work, we have developed a holonomic mobile mechanism capable of running over steps. The mechanism realizes omni-directional motion on a flat floor and passes over uneven ground in forward and backward directions. The vehicle has seven special wheels with cylindrical free rollers and two passive body axes that can adapt to rough terrain. Seven actuators are located in each wheel; therefore, our vehicle system requires the rotation velocity of each wheel to be coordinated. However, it is difficult to keep such coordination among the wheels — as the vehicle passes over the step, the load applied to the wheel tends to heavy and irregular. Therefore, we propose a new control system for synchronization among the wheels. In this paper, the following two topics are discussed: the load adjustment so as not to exceed the maximum torque of the actuator in some of the wheels and keeping the balance of rotation velocity among the wheels. Our novel control method adjusts the output value by referring to the state of the other wheels. The performance of our system is investigated by means of computer simulations and experiments using our prototype vehicle.     

Worm wheel mechanism with passive rollers

In this study, we developed new worm wheel mechanisms with passive rollers as their teeth and confirmed useful functions of these worm wheels with passive rollers to transmit power from worm gears with higher energy efficiency than ordinary worm wheels. By using passive rollers as their teeth, the developed worm wheels could realize high-power transmission efficiency with rolling frictional resistance instead of sliding frictional resistance. A worm wheel with conical passive rollers and one with disk-shaped passive rollers was fabricated as prototypes and examined in experiments. Smooth back-drivability of the worm wheels with passive rollers, which is difficult to realize with conventional worm wheels, was also demonstrated in the experiments. These serial experiments revealed that the developed worm wheel mechanism with passive rollers can replace conventional worm wheels with the same number of teeth and module in ordinary power transmission mechanisms with worm gearing and realize higher energy efficiency and smooth back-drivability. These features can be very useful to realize safe and soft actuators for automation systems in a human environment.     

机械自适应管道机器人的机构原理与仿真分析

针对轮式管道机器人在遇到弯管或不规则管时会发生运动干涉的问题,提出将三轴差动轮系引入管道机器人驱动系统中,使轮式管道机器人具有对管道环境的自动适应性能,并对机械自适应管道机器人的机械结构进行了设计与研究．同时,对管道机器人进行了三维建模及运动仿真分析,验证了应用三轴差动轮系的管道机器人具有较强的弯管适应能力及管内运动的稳定性．该机器人具有适应能力强、结构紧凑、驱动效率高、工作可靠及成本低的特点．     

Experimental verification of a design methodology for torsion actuators based on a rapid pull-in solver

In this work, an experimental and theoretical study of the effect of various geometrical parameters on the electromechanical response and pull-in parameters of torsion actuators is presented. A lumped two-degrees-of-freedom (L2DOF) pull-in model that takes into account the bending/torsion coupling, previously proposed for cantilever suspended actuators, is tailored for the torsion actuators under study. This model is shown to better capture the measured pull-in parameters than previously proposed lumped single-degree-of-freedom (L1DOF) models. The measurements were conducted on torsion actuators with various shapes, fabricated on silicon-on-insulator (SOI) wafers using deep reactive ion etching (DRIE) and flip-chip bonding. Furthermore, a novel rapid solver, for extracting the pull-in parameters of the L2DOF model of the torsion actuators, is proposed. The proposed solver is based on a Newton-Raphson scheme and the recently presented DIPIE algorithm and is shown to be /spl sim/10 times faster than the prevalent voltage iterations based solvers. The rapid and more accurate pull-in extraction of the proposed approach renders it as a tool for extensive analysis and design optimization of torsion actuators.     

矩形布置滑板输送机内饰线动力学仿真分析

针对滑板输送机容易出现主驱动摩擦轮打滑即驱动力不足的问题,采用脚本语言建模方法,自动完成滑板输送机内饰线动力学仿真模型的建立和分析条件的设定,并将输送线上的阻力条件转化为滚动摩擦摩阻力偶施加至仿真模型中,获得内饰线在连续输送条件下突然启动时所需最大摩擦驱动力和连续工作时所需稳定摩擦驱动力的大小.通过验证,摩擦轮弹簧压紧力满足设计要求.分析结果可为滑板输送机的整体设计和摩擦驱动轮的详细设计提供参考.     

电机故障对月球车驱动轮牵引性能的影响

月球车是一种在外太空极端恶劣环境下长时间自主运行、不可维修的轮式移动机器人,为准确预测车轮驱动电机故障运行时的牵引性能对于月球车的可靠性有重要意义。为确保月球车顺利完成任务,建立了电机正常运行时的电磁场仿真模型,在模型基础上针对开关管短路、开关管开路、霍尔位置信号恒值和绕组开路等分别建立了故障仿真模型,通过仿真确定了能够识别各种故障的特征波形,并绘制了电机的机械特性曲线。应用车辆地面力学理论对比分析了电机正常与故障运行时驱动轮牵引性能的变化。研究结果表明,当电机发生各种故障后,驱动轮的牵引性能均有不同程度的下降。可为带障运行条件下的多轮协调控制策略的制定提供了理论依据。     

Microfabricated torsional actuators using self-aligned plastic deformation of silicon

In this paper, we describe angular vertical-comb-drive torsional microactuators made in a new process that induces residual plastic deformation of single-crystal-silicon torsion bars. Critical dimensions of the vertically interdigitated moving-and fixed-comb actuators are self-aligned in the fabrication process and processed devices operate stably over a range of actuation voltages. We demonstrate MEMS scanning mirrors that resonate at 2.95kHz and achieve optical scan angles up to 19.2 degrees with driving voltages of 40V/sub dc/ plus 13V/sub pp/. After continuous testing of five billion cycles at the maximum scanning angle, we do not observe any signs of degradation in the plastically deformed silicon torsion bars.     

A MEMS-based tracking milli-mirror for high-density optical disk drives

We present a new MEMS-based milli-mirror for precise tracking in high-density optical disk drives (ODDs). The device consists of a torsionally suspended mirror plate, one pair of torsion springs, which support the mirror plate and offer a restoring torque, and two pairs of electrodes attached to the mirror plate and glass substrate. The dimensions of mirror plate and torsion springs were determined so that a 5 V dc bias ±4.5 V ac drive voltage would provide the mirror with ±0.02° rotation to transmit laser beam spot on spinning disk. The MEMS-based milli-mirror was successfully fabricated using MEMS technology. Displacement–voltage linearization scheme was implemented by differential voltage driving. The static and dynamic performances of mirror prototype, such as capacitance versus driving voltage, rotation angle versus driving voltage, and resonant frequency were characterized and compared well with the simulation solutions. The mechanical resonant frequency of the mirror is expected to be high enough to satisfy the requirement of the servo bandwidth of precise tracking-control in high-density blue-laser optical disk drive.     

Motion Control of Passive Intelligent Walker Using Servo Brakes

We propose a new intelligent walker based on passive robotics that assists the elderly, handicapped people, and the blind who have difficulty in walking. We developed a prototype of the robot technology walker (RT walker), a passive intelligent walker that uses servo brakes. The RT walker consists of a support frame, two casters, two wheels equipped with servo brakes, and it has passive dynamics that change with respect to applied force/moment. This system is intrinsically safe for humans, as it cannot move unintentionally, i.e., it has no driving actuators. In addition, the RT walker provides a number of navigational features, including good maneuverability, by appropriately controlling the torque of servo brakes based on RT. We propose a human adaptive motion control algorithm that changes the apparent dynamics to adapt to user difficulties, and an environmentally adaptive motion control algorithm, which incorporates environmental information to provide obstacle/step avoidance and gravity compensation functions. The proposed control algorithms are experimentally applied to the RT walker to test their validity.     

Low-voltage, large-scan angle MEMS analog micromirror arrays with hidden vertical comb-drive actuators

This paper reports on novel polysilicon surface-micromachined one-dimensional (1-D) analog micromirror arrays fabricated using Sandia's ultraplanar multilevel MEMS technology-V (SUMMiT-V) process. Large continuous DC scan angle (23.6/spl deg/ optical) and low-operating voltage (6 V) have been achieved using vertical comb-drive actuators. The actuators and torsion springs are placed underneath the mirror (137/spl times/120 /spl mu/m/sup 2/) to achieve high fill-factor (91%). The measured resonant frequency of the mirror ranges from 3.4 to 8.1 kHz. The measured DC scanning characteristics and resonant frequencies agree well with theoretical values. The rise time is 120 /spl mu/s and the fall time is 380 /spl mu/s. The static scanning characteristics show good uniformity (相似文献   

A methodology and model for the pull-in parameters of magnetostatic actuators

Magnetostatic actuators exhibit bistability similarly to the pull-in phenomena of electrostatic actuators. In this paper a methodology and model for the extraction of the magnetic Pull-In parameters of magnetostatic actuators are derived. The flux-controlled magnetostatic actuator is analyzed based on the energy representation and the magnetomotive force-controlled magnetostatic actuator is analyzed in the thermodynamic potential energy (or co-energy) representation. An algebraic equation, referred to as the magnetic Pull-In equation, for each of the two cases (flux-controlled and magnetomotive force-controlled actuators) is derived. By solving these Pull-In equations either analytically or numerically, the magnetic Pull-In parameters are obtained. Several case studies, covering displacement and torsion magnetic actuators, are presented and analyzed, illustrating the usefulness of the proposed methodology, its relative simplicity as well as the adaptability and practical usage in wide spectrum of magnetic actuators. [1425].     

An angle-based design approach for rectangular electrostatictorsion actuators

In this paper, we develop a fast, angle-based design approach for rectangular electrostatic torsion actuators based on several simple equations. This approach is significantly more straightforward than the usual full calculation or simulation methods. The main results of the simplified approach are verified by comparing them with analytical calculations and MEMCAD simulations with fractional difference smaller than 3% for torsion mode dominant actuators. Also, good agreement is found by comparison with the measured behavior of a microfabricated full-plate device     

Study of the internal dynamics of an autonomous mobile robot

The requirement of ideal rolling without sideways slipping for wheels imposes nonholonomic (non-integrable) constraints on the motion of the wheels and consequently on the motion of wheeled mobile robots. From the control point of view, the dynamics of nonholonomic systems can be divided in two parts: external and internal dynamics. The dimension of the external dynamics of nonholonomic systems depends on the number of inputs to the system and the dimension of the internal dynamics depends on the number of independent nonholonomic constraints. For different motion control problems of nonholonomic systems, a smooth (model based) state feedback control law only deals with the system external dynamics; therefore, the system internal dynamics must be examined separately and its stability has to be analyzed and proved.In this paper, the internal dynamics of a three-wheel mobile robot with front wheel steering and driving is investigated. In particular, its internal dynamics stability is analyzed for two different situations, when the mobile robot is moving and when it is stationary.     

Development of Three-Dimensional Microstages Using Inclined Deep-Reactive Ion Etching

Three-dimensional (3-D) microstages driven by electrostatic comb actuators that provide continuous motion along three axes (x,y , and z ) were designed and fabricated. Each 3-D microstage consisted of sets of traveling tables, suspension systems, and comb actuators. To convert lateral displacement of the comb actuators to vertical motion, one suspension system incorporated leaf springs inclined to a substrate. To efficiently construct the inclined leaf springs, we devised a fabrication technique that uses deep reactive ion etching. Three-dimensional microstages were then fabricated in a 20-mum-thick device layer on a silicon-on-insulator wafer. The maximum vertical (z) displacement of this 3-D microstage was 2.6 mum, and the maximum lateral displacement (x and y) was more than 6 mum in each direction, achieved by using support suspensions to suppress the interference between the comb actuators. A 3-D microstage was then installed in a commercial atomic force microscope, and a 3-D image of a grating was successfully measured without hysteresis using this 3-D microstage as the scanning device.     

A Modular Fuzzy Control Approach for Two-Wheeled Wheelchair

Wheelchairs on two wheels are becoming essential part of life for disabled persons. But designing control strategies for such wheelchairs is a challenging task due to the fact that they are highly nonlinear and unstable systems. The subtle design of the system mimics a double inverted pendulum with three actuators, one for each wheel, and one for chair position. The system starts to work with lifting the front wheels (casters) to the upright position and further with stabilizing in the upright position. The challenge resides in the design and implementation of suitable control strategies for the two-wheeled wheelchair so as to perform comparably similar to a normal four-wheeled wheelchair. A two-level modular fuzzy logic controller is proposed in this paper. A model of the standard wheelchair is also developed as a test and verification platform using Visual Nastran software integrated with Matlab.     

Physically based real-time interactive assembly simulation of cable harness

In this paper, we designed and developed an interactive assembly simulation system of cable harness. First, we establish a real-time physical model of cable harness based on an extension of the mass–spring model. We use various kinds of springs to describe the different properties of the cable harness: linear springs for stretching, bending springs for bending, and torsion springs for geometrical torsion and material twisting. The constraints of connectors and clips on cable harness are both considered. We also associate the elastic coefficients of various springs with the material parameters of the cable. Moreover, we use spherical bounding volume hierarchy and triangular facets for collision detection of cable harness during the assembly simulation. By applying contact forces to both ends of the cable links that collide with the surrounding environment, we obtain the real-time contact response of cable harness. Finally, we apply the proposed model to a cable assembly task. The results show that the proposed model successfully expressed the deformation of the cable harness and the interactive manipulation is computationally efficient.