Motion control

A linear stage or ‘Linear Slide’ as it is mostly called is one of the components found in precision motion systems. It is more of a restrictive component as it limits the movement of an object to a single axis or direction. They are slides that provide a more controlled and distinct positioning for objects along the linear axis of its pathway. They are applied in various forms of automated machinery. Linear Stages are like navigation systems for these machinery and their job is to set them in tune with their axes. Now, with this restriction in movement of these motion systems, you can expect lots of friction, energy loss of even a stick and slip situation. However, they do make use of some linear bearing methods to alleviate these minor issues.

A population based real-time optimization method for tuning dynamic position control parameters of robot manipulators has been proposed. Conventionally, the positional control is achieved by inverse dynamics feedforward and PID feedback controllers. The proposed method allows to tune the PID controller parameters using population based optimization methods to minimize the error while tracking a repeated desired trajectory on real-time. The stability of the system is granted by switching the inappropriate settings to a stable default using a real-time cost evaluation function. The proposed tuning method is tested on a two-joint planar manipulator with Cross-Entropy optimization, and on a planar inverted pendulum both with Cross Entropy, and Differential Evolutionary search methods. The test results indicated that the proposed method improves the settling time and reduces the position error over the repeated paths for both population based evolutionary optimization. Index Terms-adaptive control, PID tuning, real-time CE optimization, real-time evolutionary optimization, real-time DE optimization.

In this paper we propose digital control methods for steering real analytic controllable systems between arbitrary state configurations. The main idea is to achieve a multirate sampled procedure to perform motions in all the directions of controllability under piecewise constant controls. When it is applied to nonholonomic control systems without drift, the procedure simplifies. In particular, it results in exact steering on chained systems recently introduced in the motion planning literature. A classical example is reported.

This manuscript examines the evolution of internet value systems in the motion control industry. We believe the primary reason behind the inconsistent performance of that industry's adoption of the internet in the supply channel was largely due to poor strategy. Using a the concepts of bias exchanges and game theory it is suggested that internet strategies such as disintermediation and first-mover advantage were elusive because firms focused too much on technology and not enough on customer value. Lessons for managers and future decisions are offered.

Camless internal combustion engines offer improvements over traditional engines in terms of torque performance, reduction of emissions, reduction of pumping losses and fuel economy. Theoretically, electromagnetic valve actuators offer the highest potentials for improving efficiency due to their control flexibility. For real applications, however, the valve actuators developed so far suffer from high power consumption and other control problems. One key point is the design of the reference trajectory to be tracked by the closed loop controller. In this brief, a design technique aimed at minimizing power consumption is proposed. A constrained optimization problem is formulated and its solution is approximated by exploiting local flatness and physical properties of the system. The performance of the designed trajectory is validated via an industrial simulator of the valve actuator.

We report on our empirical studies of a new controller for a two-link brachiating robot. Motivated by the pendulum-like motion of an ape's brachiation, we encode this task as the output of a "target dynamical system." Numerical simulations indicate that the resulting controller solves a number of brachiation problems that we term the "ladder," "swing-up," and "rope" problems. Preliminary analysis provides some explanation for this success. The proposed controller is implemented on a physical system in our laboratory. The robot achieves behaviors including "swing locomotion" and "swing up" and is capable of continuous locomotion over several rungs of a ladder. We discuss a number of formal questions whose answers will be required to gain a full understanding of the strengths and weaknesses of this approach.

A globally convergent adaptive control scheme for robot motion control with the following features is proposed. First, the adaptation law possesses enhanced robustness with respect to noisy velocity measurements. Second, the controller does not require the inclusion of high gain loops that may excite the unmodeled dynamics and amplify the noise level. Third, we derive for the unknown parameter design a relationship between compensator gains and closed-loop convergence rates that is independent of the robot task. A simulation example of a two-DOF manipulator features some aspects of the control scheme.

In this paper a new intelligent identification method of uncertainty bound utilizes an adaptive neurofuzzy inference system (ANFIS) in a feedback scheme is proposed. The proposed ANFIS feedback structure performs better in determining the uncertainty bounds with minimum number of iterations and error. In our proposed technique, the intelligent identified uncertainty weighting function is validated utilizing v-gap to ensure the stability of the designed H controlled system. Our proposed intelligent identification of uncertainty bound is demonstrated on a servo motion system. Simulation and experimental results show that the new ANFIS identifier is more reliable and highly efficient in estimating the best uncertainty weighting function for robust controller design.

In this paper an operational model for the automatic generation of lifelike gestures of an anthropomorphic virtual agent is described. The biologically motivated approach to controlling the movements of a highly articulated figure provides a transformation of spatiotemporal gesture specifications into an analog representation of the movement from which the animations are directly rendered. To this end, knowledge-based computer animation techniques are combined with appropriate methods for trajectory formation and articulated figure animation.

Multiple view 3D video reconstruction of actor performance captures a level-of-detail for body and clothing movement which is time-consuming to produce using existing animation tools. In this paper we present a framework for concatenative synthesis from multiple 3D video sequences according to user constraints on movement, position and timing. Multiple 3D video sequences of an actor performing different movements are automatically constructed into a surface motion graph which represents the possible transitions with similar shape and motion between sequences without unnatural movement artefacts. Shape similarity over an adaptive temporal window is used to identify transitions between 3D video sequences. Novel 3D video sequences are synthesized by finding the optimal path in the surface motion graph between user specified key-frames for control of movement, location and timing. The optimal path which satisfies the user constraints whilst minimizing the total transition cost between 3D video sequences is found using integer linear programming. Results demonstrate that this framework allows flexible production of novel 3D video sequences which preserve the detailed dynamics of the captured movement for actress with loose clothing and long hair without visible artefacts.

This paper introduces biohybrid microsystems actuated by cardiomyocytes, such as microcantilever, microrobot, and micropump. The microfabicated biohybrid microcantilever can measure the contractile force of self-organized cardiomyocytes. The microcantilever is made of a biocompatible PDMS substrate, using a simple microfabrication technique and a specially designed 3D micromolding aligner. The contractile force of the cardiomyocytes makes a bending displacement of the microcantilever. Conversely, from the displacement, we can estimate the contractile of the cardiomyocytes on the microcantilever. The bending motion of the microcantilever can be applied as a biohybrid actuator of microrobot. We have developed a novel method to fabricate a crab-like microrobot that can actuate for a long period under a physiological condition. The microrobot consists of three separate front and rear legs which have a shape of the microcantilever. The performance of our crab-like microrobot was measured at an average velocity of 100 μ m/s, and the estimated total distance it traveled was 50 m for a one-week period. Finally, a micropump actuated by the self-beating cardiomyocytes is fabricated and the pumping performance is demonstrated.

Ahstract-In this paper, a software simulation model is developed for a two wheels driven mobile robot motion controller that can navigate the robot safely through an unknown environment. The work involves the design of a controller, which has four functions: motion control; obstacle avoidance; self-location; and path planning both global and local. The proposed controller is responsible for the mobile robot navigation after it generates a trajectory between start and goal points. Also it enables the robot to operate successfully in the presence of various obstacles present in any user built maps. The mobile robot is able to locate its position on any given map. The dynamic of the mobile robot is examined and the time constant of the two motors, which affects the direction of the mobile robot motion, is controlled. Obstacle avoidance is implemented with Fuzzy Logic Controller. The numerical experiments demonstrated that the indoor robot navigated successfully in tight corridors, avoided obstacles and dealt with a variety of world maps with various irregular wall shapes that were presented to it.

Underwater glider is an autonomous underwater vehicle that glides by controlling their buoyancy and attitude using internal actuators. By changing the vehicle's buoyancy intermittently, vertical motion can be achieved. Characteristics of glider motion include upward and downward movement in a saw tooth pattern, turning and gliding in a vertical spiral motion and gliding without using thrusters or propellers. This paper presents the modelling and identification on net buoyancy, depth and pitching angle of an underwater glider system. A ballast tank subsystem is considered appropriate for the identification process since it is the main parameter for the motion control. By selecting the ballast rate as the input, three aspects of the dynamics of a glider can be observed: buoyancy, depth of the glider and pitching angle. The MATLAB System Identification Toolbox TM is used to obtain a mathematical model of the glider ballast-buoyancy, ballast-depth and ballast-pitching angle conditioning system. The best three parametric estimation models are chosen, and the results of the comparison between simulated and estimated outputs are presented. The information obtained from the modelling and identification approaches are used for USM's Underwater Glider Prototype controller design. The information observed during this procedure are utilised for optimisation, stability, reliability and robustness analysis of the underwater glider.

This paper addresses the problem of grasping and manipulating a polygonal object with three discshaped robots capable of translating in arbitrary directions in the plane. The main novelty of the proposed approach is that it does not assume that contact is maintained during the execution of the grasping/manipulation task. Nor does it rely on detailed (and a priori unveri able) models of friction or contact dynamics. Instead, the range of possible object motions for a given position of the robots is characterized in con guration space. This allows the construction of manipulation plans guaranteed to succeed under the weaker assumption that jamming does not occur during the task execution.

To solve problems of traffic saturation in cities, new alternative "Urban Transportation Systems" are based on electric vehicles in free-access. One necessary functionality of such systems is their ability to move in a platoon fashion. Platooning of these automatic guided vehicles, relying on RTK-GPS sensors and inter-vehicles communication, is addressed in this paper. The developed control law is based on a global control strategy; actually, it can take into account all the platoon state, and not only the immediate previous vehicle state. Distance here is understood as difference of curvilinear abscissa along a reference trajectory. Relying on nonlinear control theory, lateral and longitudinal control are fully decoupled, and therefore addressed independently. To ensure passengers comfort, additional monitoring functions supervise our control system. Then, experiment, carried out with urban vehicles, and simulations of long platoon, are presented.

This paper describes how an underwater vehicle can control its motion by sensing the surrounding flowfield and using the sensor measurements in a dynamic feedback controller. Limitations in existing sensing modalities for flowfield estimation are mitigated by using a fish-inspired distributed sensor array and a nonlinear observer. Estimation performance is further increased by optimizing sensor placement on the vehicle body. We optimize sensor placement along a streamlined body using measures of flowfield observability, namely the empirical observability gramian. Velocity potentials model the flow around the vehicle and a recursive Bayesian filter estimates the flow from noisy velocity measurements. To orient the body into the oncoming flow (a fish-inspired behavior known as rheotaxis) we implement a dynamic, linear controller that uses the estimated angle of attack. Numerical simulations illustrate the theoretical results.

This paper proposes an architecture for motion capture based animation systems, which works with several data formats and uses the building block paradigm for motion processing operations. Also, a user interface is proposed to perform an intuitive visualization of the animation main elements. A prototype system has been implemented, based on the presented concepts, and its operation is discussed.

This paper represents an ongoing investigation of dexterous and natural control of upper extremity prostheses using the myoelectric signal (MES). The scheme described within uses pattern recognition to process four channels of MES, with the task of discriminating multiple classes of limb movement. The method does not require segmentation of the MES data, allowing a continuous stream of class decisions to be delivered to a prosthetic device. It is shown in this paper that, by exploiting the processing power inherent in current computing systems, substantial gains in classifier accuracy and response time are possible. Other important characteristics for prosthetic control systems are met as well. Due to the fact that the classifier learns the muscle activation patterns for each desired class for each individual, a natural control actuation results. The continuous decision stream allows complex sequences of manipulation involving multiple joints to be performed without interruption. Finally, minimal storage capacity is required, which is an important factor in embedded control systems.

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The flexibility required of an agile manufacturing system must be achieved largely through computer software. The system's control software must be adaptable to new products and to new system components without becoming unreliable or difficult to maintain. This requires designing the software specifically to facilitate future changes. As part of the Agile Manufacturing Project at Case Western Reserve University, we have developed a software architecture for control of an agile manufacturing workcell, and we have demonstrated its flexibility with rapid changeover and introduction of new products. In this paper, we describe the requirements for agile manufacturing software and how our software architecture addresses them.

In the automation world the intelligent electrical devices need to be accurately synchronized for time stamping of data and motion control. In this paper we discuss how to achieve precise time synchronization over switched Ethernet networks in a generic way. The addressed synchronization requirements relate to substation automation, which is associated with five levels of synchronization accuracy defined as the IEC 61850 classes T1 to T5. The paper challenges the hardest requirements and present general solutions for IEC classes T4/T5 (4µ µ µ µs/1µ µ µ µs) and

Unmanned underwater vehicles (UUVs) have become an integral part in helping humans do underwater explorations more efficiently and safely since these vehicles can stay underwater much longer than any human can possibly do and they require little or almost no human interaction. These vehicles are subject to dynamic and unpredictable nature of the underwater environment resulting to complexities in their navigation. This paper proposes a fuzzy logic-based controller to allow the vehicle to navigate autonomously while avoiding obstacles. The said controller is implemented in an actual low-cost underwater vehicle equipped with magnetometer and ultrasonic sensors. The intelligence of the UUV includes a two fuzzy logic block, namely Motion Control block and Heading Correction block. The fuzzy logic controller takes in target positions in X, Y and Z axes. Also, the heading error and rate of heading error are included as inputs in order to correct the bearing or direction of the vehicle. A ...

In recent years, the realization of a haptic system has been desired strongly in the fields of medical treatment and expert's skill acquisition. An integrated system design of the analysis of the interaction between a robot and the environment required for stable contact operation, an observation method of the reaction force from the environment, and the architecture of a bilateral control system are absolutely essential for acquisition and reproduction of a vivid tactile sensation. In this paper, a haptic training system is realized based on multilateral control. The law of action and reaction is attained by three robots. Bilateral control is extended, and multilateral control is introduced. Multilateral control is designed similarly as bilateral control based on modal decomposition; force is controlled in the common mode, and position is controlled in the differential mode. The scaling factors of position and force are set independently. Therefore, it is possible to change a trainer's assistant force according to a trainee's skill level. The proposed training system based on multilateral control will be a fundamental technology for the evolution of haptic devices.

This paper presents two novel six-axis magnetic-levitation (maglev) stages capable of nanoscale positioning. These stages have very simple and compact structures, which is advantageous to meet the demanding positioning requirements of next-generation nanomanipulation and nanomanufacturing. Six-axis motion generation is accomplished by the minimum number of actuators and sensors. The first-generation maglev stage, namely the -stage, is capable of generating translation of 300 m and demonstrates position resolution better than 2 nm root-mean-square (rms). The second-generation maglev stage, namely the Y-stage, is capable of positioning at a resolution better than 3 nm rms over a planar travel range of 5 mm × 5 mm. A novel actuation scheme was developed for the compact structure of this stage that enables six-axis force generation with just three permanent-magnet pieces. This paper focuses on the design and precision construction of the actuator units, the moving platens, and the stationary base plates. The performance of the two precision positioners is compared in terms of their positioning and load-carrying capabilities and ease of manufacture. Control system design for the two positioners is discussed and an experimental plant transfer function model is presented for the Y-stage. The superiority of the developed instruments is also demonstrated over other prevailing precision positioning systems in terms of the travel range, resolution, and dynamic range. The potential applications of the maglev positioners include semiconductor manufacturing, microfabrication and assembly, nanoscale profiling, and nanoindentation.

Nine chronic stroke subjects trained over a period of 6 weeks, with 3 one-hour sessions of robot-assisted therapy per week, consisting in two exercises requiring active participation pro-moted by therapeutic games. Behavioral data collected by the Haptic Knob were ...

presents an open-architecture Computerized Numerical Control (CNC) system based on Windows CE, which is a multi-task embedded real-time operating system. The CNC system adopts a master-slave architecture, And the Master applies with Windows CE, which charges weak real-time tasks such as NC code's editor, interpreter and simulator function block, fault diagnosis, 11O monitoring and control etc, while the slave adopts a motion control card based on Digital Signal Processor (DSP) and Field Programmable Gate Array (FPGA), which charges hard realtime tasks including interpolation, electromotor control etc. The research realizes the construction of hardware and software of CNC system and solves such core issues as NC code interpreter and simulation, Rate Monotonic Scheduling (RMS) task schedule algorithm and task scheduling of CNC system. The experimental results have proven the development of CNC system based on Windows CE is a feasible, novel and fast technology course in the field of CNC.

The article deals with the analysis and interpretation of dynamic scenes typical of urban driving. The key objective is to assess risks of collision for the ego-vehicle. We describe our concept and methods, which we have integrated and tested on our experimental platform on a Lexus car and a driving simulator. The on-board sensors deliver visual, telemetric and inertial data for environment monitoring. The sensor fusion uses our Bayesian Occupancy Filter for a spatio-temporal grid representation of the traffic scene. The underlying probabilistic approach is capable of dealing with uncertainties when modeling the environment as well as detecting and tracking dynamic objects. The collision risks are estimated as stochastic variables and are predicted for a short period ahead with the use of Hidden Markov Models and Gaussian processes. The software implementation takes advantage of our methods, which allow for parallel computation. Our tests have proven the relevance and feasibility of our approach for improving the safety of car driving.

This paper utilizes the idea of "robot ergonomics" in which robotic tasks are evaluated according to ergonomics criteria. Robot performance is continuously reeorded in terms of total motion for each robotic link, the load applied on each joint, and the accuracy of each motion. Evaluating robot motion can assist in the design of a robotic cell, where robot position and layout of peripheral equipment are determined. In previous work, the main measure has been AJU (Arm Joint Utilization). Two new measures are developed here: AJA (Arm Joint Accuracy) and AJL (Arm Joint Load). A test case of an articulated industrial robot, performing a kiting task is presented. Robot performance is evaluated for various bin positions, and based on these results, the bin position relative to the robot is determined based on all three measures, AJA, AJL and AJU. 0-7803-4300-x-5/98 $10.00

This paper reports high-precision motion control at the target position and the offline compensation of the straightness error occurring during the motion of the magnetically levitated stage supported by the linear magnetic bearing. The linear magnetic bearing is composed of electromagnets and sensors in the same module to enable easy maintenance and to reduce the machining error, and the conventional

This paper describes the control of an electric wheel chair with voice commands. This chair has been developed and built at the U.A.H. Electronic Department and financed by the ONCE Fotmdation (Spain). The first prototype consists of voice recosnition, motor control, user interface and central processor modules. The electronic system allows the chair user a safe, easy ride, and guarantees the concordance between user commands and actual trajectories. Furthermore, the system has been designed to allow the addition of future features, like obstacle and stair detection and the tele.-commanding of electrical household appliances from the chair.

A piston motion controller for a free-piston internal combustion engine is presented. To improve dynamic performance in the control of the piston motion and engine compression ratio, the controller response is determined from a prediction of engine top dead centre error rather than the measured value from the previous cycle. The proposed control approach showed superior performance compared with that of standard PI feedback control known from the literature due to a reduced control action time delay. The manipulation of fuel injection timing to reduce in-cylinder pressure peaks and cycle-to-cycle variations was also studied, indicating that with the the piston motion estimation, the injection timing is a powerful control variable for this purpose.

Summary Virtual humans are the computer representation of real humans in virtual worlds. Human representation in virtual worlds is vital as people are central elements of the real and virtual worlds. Animating virtual humans remains a challenging task due to the large number of degrees of freedom in the human skeleton, the ability of human observers to detect unnatural movements, and the complexity of realistic appearance and behaviour. The difficulty of the problem has resulted in research into many subproblems of human ...

Underwater glider is an autonomous underwater vehicle that glides by controlling their buoyancy and attitude using internal actuators. By changing the vehicle's buoyancy intermittently, vertical motion can be achieved. Characteristics of glider motion include upward and downward movement in a saw tooth pattern, turning and gliding in a vertical spiral motion and gliding without using thrusters or propellers. This paper presents the modelling and identification on net buoyancy, depth and pitching angle of an underwater glider system. A ballast tank subsystem is considered appropriate for the identification process since it is the main parameter for the motion control. By selecting the ballast rate as the input, three aspects of the dynamics of a glider can be observed: buoyancy, depth of the glider and pitching angle. The MATLAB System Identification Toolbox TM is used to obtain a mathematical model of the glider ballast-buoyancy, ballast-depth and ballast-pitching angle conditioning system. The best three parametric estimation models are chosen, and the results of the comparison between simulated and estimated outputs are presented. The information obtained from the modelling and identification approaches are used for USM's Underwater Glider Prototype controller design. The information observed during this procedure are utilised for optimisation, stability, reliability and robustness analysis of the underwater glider.

The IEC 61499 standard enhances the 1131 Function Block (FB) concept to support the development of open, interoperable, distributed control applications. The first prototype software tools that support the FB model have already appeared in the market. The industry shows a growing interest in the function block model but more research and reference implementations are required to investigate and demonstrate the applicability of the new paradigm in this domain. In this paper the applicability of the IEC 61499 model in a well known PID-based control application for robotic arms is examined. To prove the correctness of the FB-based design specs, a specific code generator was developed to automatically produce the executable model of the application for a prototype Linux-based FB execution environment. The system was demonstrated successfully, proving the effectiveness of the FB model as well as the usability of the proposed execution environment.

In recent years, it is remarkable to see the increasing number of studies related to the theory and application of fractional order controller (FOC), specially controller, in many areas of science and engineering. Research activities are focused on developing new analysis and design methods for fractional order controllers as an extension of classical control theory. In this paper, a new tuning method for fractional order proportional and derivative ( ) or FO-PD controller is proposed for a class of typical second-order plants. The tuned FO-PD controller can ensure that the given gain crossover frequency and phase margin are fulfilled, and furthermore, the phase derivative w. r. t. the frequency is zero, i.e., the phase Bode plot is flat at the given gain crossover frequency. Consequently, the closed-loop system is robust to gain variations. The FOC design method proposed in the paper is practical and simple to apply. Simulation and experimental results show that the closed-loop system can achieve favorable dynamic performance and robustness.

A new digital control solution to motion control problems is proposed. It is based on a unique active disturbance rejection concept, where the disturbances are estimated using an extended state observer (ESO) and compensated in each sampling period. The dynamic compensation reduces the motion system to approximately a double integrator which can be easily controlled using a nonlinear proportional-derivative controller. The proposed Active Disturbance-Rejection Controller (ADRC) consists of the ESO and the nonlinear PD controller and is designed without an explicit mathematical model of the plant. Hence the controller is inherently robust against plant variations. Through simulation, frequency response analysis, and hardware tests, it is shown that the proposed approach is superior to the current PID based technology. It stands out especially in handling set point change, large inertia and friction variations, and external torque disturbance, all of which is seen as "disturbance" by ADRC and is actively compensated. The improvement in transient response and steady state error is also quite evident.

This paper addresses the problem of path generation and motion control for the autonomous maneuver of a farm vehicle with a trailed implement in headland. A reverse turn planner is firstly investigated, based on primitives connected together to easily generate the reference motion. Then, both steering and speed control algorithms are presented to accurately guide the vehicle-trailer system. They are based on a kinematic model extended with additional sliding parameters and on model predictive control approaches. Real world experiments have been carried out on a low friction terrain with an experimental mobile robot pulling a trailer. At the end of each row, the reverse turn is automatically generated to connect the next reference track, and the maneuver is autonomously performed by the vehicle-trailer system. Reported experiments demonstrate the capabilities of the proposed algorithms.

A new method using non-linear H 1 and sliding mode control (SMC) is presented for a permanent magnet synchronous motor (PMSM) position control system. It is a high-performance controller in the presence of motor parameters variations and unknown load torque disturbances. In the proposed technique, the load torque is considered as an external disturbance and non-linear H 1 is utilised to minimise its influence on the rotor position. Although H 1 is to some extend robust against motor parameter variations, parameter variations may affect the performance of H 1 controller, so SMC is used to reject these variations. Integration of these two methods offers an efficient robust position controller for PMSM. Position control of PMSM using the proposed method is compared with those obtained by other methods. Merits of the approach through simulations are verified by the experimental results.