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This note presents a unified approach to nominal control generation and return map parameterization for yo-yo playing. The approach is based on choosing an intermediate state of the yo-yo as the parameter and formulating an optimization problem with appropriate boundary conditions that incorporate the corresponding parameter. By solving the optimization problems, both the return map and the nominal optimal control for the robot can be obtained. The return map is naturally parameterized with the intermediate state, which can be treated as a virtual control. The return map facilitates the application of standard analysis and design methods for discrete-time control systems. The approach is promising as it might be extended to control other cyclic dynamic systems. Index Terms--Manipulation planning, motion control, optimal control, robotic juggling.

This paper discusses velocity measurement for motor drives with optical encoders. Although many methods on velocity measurement have been proposed, accurate measurement was not achieved in a high-speed range. This paper therefore proposes synchronous-measurement method (S method) that measures the velocity synchronized with the alteration of pulse numbers in each sampling period. Accurate velocity measurement is achieved in all speed ranges with this method. Furthermore, other velocity prediction methods are applicable in addition to the method. Simulation and experimental results verify the validity of the proposed method. Index Terms--Acceleration control, mechatronics, motion control, optical encoder, tachometers, velocity measurement.

Swedish wheeled robots have received growing attention over the last few years. Their kinematic models have interesting properties in terms of mobility and possible singularities. This paper addresses the issue of kinematic modeling, singularity analysis, and motion control for a generic vehicle equipped with N Swedish wheels. Index Terms--Mobile robot kinematics, mobile robots, motion control, wheeled robots.

In a free-flight airspace environment, pilots have more freedom to choose user-preferred trajectories. An onboard pilot support system is needed that exploits travel freedom while maintaining spatial separation with other traffic. Ecological interface design is used to design an interface tool that assists pilots with the tactical planning of efficient conflict-free trajectories toward their destination. Desired pilot actions emerge from the visualization of workspace affordances in terms of a suitable description of aircraft (loco)motion. Traditional models and descriptions for aircraft motion cannot be applied efficiently for this purpose. Through functional modeling, more suitable locomotion models for trajectory planning are analyzed. As a result, a novel interface, the state vector envelope, is presented that is intended to provide the pilot with both low-level information, allowing direct action, and high-level information, allowing conflict understanding and situation awareness. Index Terms--Ecological interface design (EID), functional modeling, navigation interface, separation assistance.

This paper considers the application of a low-force robotic manipulator to guide a human user's movements to place a tool (or the user's hand) at a predetermined position or move it along a predetermined trajectory. This application is potentially useful, e.g., skill training for humans, rehabilitation, and human-machine coordination in the manufacturing industry. A proportional-derivative (PD)-type position control can be used for this application, but the parameters for the controller should be appropriately chosen for enhancing the human performance of positioning and trajectory tracking. We hypothesize that the robot's position control should be stiff and appropriately slow, i.e., the proportional gain should be high and the time constant (the ratio of the derivative gain to the proportional gain) should be appropriately large. Such characteristic has been difficult to be realized in ordinary PD position control because it requires direct high-gain velocity feedback. However, our recent technique, which is proxy-based sliding mode control (PSMC), is capable of producing such a hypothetically preferred response and allows us to empirically validate the hypothesis. The results of experiments using two distinctly different robotic devices supported the hypothesis, showing that the time constant should be set around 0.1 s rather than 0.01 and 0.5 s. Index Terms--Guidance, human-machine coordination, proxy-based sliding mode control (PSMC), time constant.

This paper presents a patient transfer apparatus between bed and stretcher. This apparatus makes it possible for the nurse to move weak, injured, or paralyzed patient from bed to stretcher, or vice versa, alone. Moreover, the suffering, stress, and uneasy feeling of the patient can be alleviated. This paper describes the specification, mechanical design, control system, and motion control of the apparatus. A special devised mechanism is developed, and a new servo system is used in this control system. The control principle and algorithm of the new servo system are proposed, and the motion-control method and safety function of the apparatus are described. The experimental results and evaluation indicated the effectiveness of this system. Index Terms--Mechanism design, motion control, patient transfer, serial communication, servo system.

Limited workspace is a challenge for all motion-based simulators, whether they are large excursion systems like the National Advanced Driving Simulator or smaller simulators utilizing only Stewart Platforms. Two approaches for addressing this challenge are nonlinear washout scaling and software displacement limiting. This paper presents new algorithms developed for these approaches. The nonlinear scaling method uses the cubic Hermite interpolation polynomial to smooth the corner in the scaled output at the limit. A software displacement limiting method that generates control signals in the table frame of reference is introduced. As a result, unwanted acceleration artifacts caused by unbalanced limiting of actuators are avoided. The methods are described, and offline simulation results using the new displacement limiting method are presented. Index Terms--Displacement control, limiting, motion compensation, motion control.

Motion control technology in an open environment will be more important. Future motion systems should interact with other systems or environments. To adapt to complicated environments and do tasks, a realization of multi-degree-of-freedom motion is necessary for human cooperating motion. This paper proposes a unified control approach for multirobot systems by interaction mode control. The proposed interaction mode control considers only interactions between systems. The interactions are abstracted by using mode quarry matrices. Since the transformed modes are independent of each other, it is possible to design a controller in decoupled modal space. This paper also proposes a novel control index named 'hybrid ratio.' Hybrid ratio is defined as the influence of external acceleration input on the acceleration response of a system. Since it is possible to realize the assigned hybrid ratio in each mode according to the task, the motion command with hybrid ratio is represented as task code. Thus, the interaction mode control is able to be treated as task kinematics. The proposed interaction mode control is applied for grasping motion by multirobot systems. The numerical and experimental results show the viability of the proposed method. Index Terms--Acceleration control, disturbance observer, haptics, hybrid control, interaction mode control, modal decomposition, motion control, multirobot systems.

This paper focuses on the realization of high-performance motion control based on acceleration control. A disturbance observer is used to construct an acceleration control system. A high sampling frequency is known to be effective for improving the performance. Characteristics of acceleration control are investigated to discuss the relationship between the performance and a sampling frequency of the system. The needs for a high sampling frequency for an output are then described. Based on these considerations, a novel multirate sampling method for the acceleration control system is proposed. An output sampling period is set shorter than an input sampling period, and control calculation is executed at each output sampling period in the method. The disturbance observer is redesigned for application to the multirate system. Stability analysis is performed to verify the validity of the proposal. Feasibility of the proposed method and its influence on the performance are also verified by experimental results. Index Terms--Acceleration control, disturbance observer, motion control, multirate control.

This paper provides systematic analysis and controller design methods for high-performance two-mass servo drives with an appraisal of the effects of supplementary filtering elements associated with practical systems. Implementation issues and the resulting performance achievable from proportional-integral, proportional-integral-derivative (PID), and resonance ratio control (RRC) controllers with regard to both closed-loop robustness and control of the process variable (load velocity), in response to a step reference speed or load-side disturbance, are presented. It is shown that the high-frequency gain of the controllers is a critical design variable for determining the resulting robustness of the closed-loop system when subject to unmodeled resonant modes, high-frequency noise from the derivative of quantized sensor signals, and process perturbations, and is strongly influenced by the location and number of filters present in the various feedback loops and, importantly, the ratio of their time constants. A complete design methodology is also presented to assign the time constants of the various loop filters, and their location, using a single user-definable variable, thereby reducing the time-consuming trial-and-error approach commonly employed using conventional tuning procedures. The technique employs both time- and frequency-domain design tools to address the conflicting requirements of robustness and control performance (overshoot, bandwidth, etc.). It is also shown that, since the PID and RRC controllers are closely related, they are theoretically able to impart identical closed-loop input-output dynamics. However, by virtue of the different feedback mechanisms employed, RRC is shown to provide superior closed-loop robustness. This paper demonstrates, and practically validates, the proposed techniques by showing significant performance enhancements from a commercial off-the-shelf servo-drive test platform. Index Terms--Acceleration control, motion control, resonance, robustness, surface acoustic wave devices, torque control, velocity control, vibration control.

This paper presents the development of a compact sixaxis magnetic levitation stage, including the design and implementation of magnetic actuators, laser interferometer motion sensors, and motion controllers. The designed travel volume of the stage is 2 x 2 x 2 mm in translation and 4[degrees] x 4[degrees] x 4[degrees] in rotation. A two-axis linear actuator, based on the magnetic Lorentz force law, was designed, and three two-axis actuators, equivalent to six single-axis actuators, were implemented to achieve six-axis actuation. A high-resolution laser interferometer measurement system was implemented and employed to measure the six-axis motion of the stage, facilitating real-time feedback control. Feedback linearization, based on rigid-body dynamics of the levitated stage, and force distribution were implemented in a computer-controlled architecture so as to establish a decoupled dynamics between the six computed inputs and the resulting six-axis motions. Constant gain controllers were then designed and implemented, according to the concept of loop shaping, for each of the six axes, and high positioning stability, 1.1 nm root mean square (RMS) for x and 0.74 nm RMS for y, has been achieved. Experimental results are presented to illustrate positioning stability, system linearity, dynamic response invariance, nano stepping, multiaxis contouring, and large rotational motion. Index Terms--Loop shaping, Lorentz force, magnetic levitation, motion control, precision control.

Vibration suppression in a motion-control system is an important problem in industry applications. Recently, a number of studies about flexible manipulators have been reported. However, there is little published on pushing operation by flexible manipulators. Contact motion to an unknown environment is difficult, because the motion system should recognize the environmental stiffness and adapt to it at the time of collision. This paper proposes a pushing control by a flexible manipulator based on a resonance ratio control. The environmental information is estimated more accurately by using a position sensitive device. The proposed method is composed of three modes: 1) approaching; 2) touching; and 3) pushing. In the approaching mode, the resonance ratio control is applied to suppress the torsional vibration. Compliance control is installed in order to relax an impact force in the touching mode. Finally, a two-step controller is proposed for the pushing mode. In the first step, friction effects are identified by a friction-torque observer. Then, the pushing operation with compensation of the stick-slip friction is controlled based on the identification results in the second step. It is possible to remove an object to a desired position. The experimental results show viability of the proposed method. Index Terms--Acceleration control, disturbance observer, flexible manipulator, friction, motion control, pushing operation, resonance ratio control, vibration control.

This paper addresses the hardware and software platforms of high-speed robot control systems, which are usually integrated with multimodal sensing, multiaxis motion, and complex algorithmic capabilities. In this paper, robot control is considered from numerical processor chip architecture, board-level features, to software development cycles. Various numerical processors ranging from general purpose processors to digital signal processors are examined. This is followed by a review of the common motion control boards. Cross platform and upward compatible software development are addressed. Finally, an example application of real-time slewing control of a high-speed industrial robot is provided. Index Terms--Command shaping, digital signal processor (DSP), motion control, robot control.

In most piezoelectric applications, including precision motion control, pressure regulation in micropumps, and force control in microactuators, there is a need to develop a model that accounts for hysteresis and describes both the electrical and mechanical properties of piezoceramics, along with the electromechanical coupling between the two domains. A model that characterizes hysteresis and the coupled electromechanical effect of the sensing and actuating signals is presented The model presented characterizes the electromechanical properties of a piezoceramic actuator when subject to variable mechanical load disturbance conditions. The model is tested under a range of voltage excitations at frequencies up to 111 Hz and is shown to offer high accuracy. [DOI: 10.1115/1.2234486]

The K2K experiment at KEK is searching for neutrino oscillations by measuring the neutrino beam flux at both a 1 kilotonne water Cherenkov detector (front detector) close to the neutrino source, and at the Super Kamiokande detector 250 km away. Part of the optical calibration of the front detector is accomplished by transmitting laser light via a fiber optic cable to a light-diffusing ball immersed in the water. A manipulator system has been built to position the ball at various locations within the water volume. A description of the mechanics and the control system is presented. Index Terms--Accelerometer, detector calibration, inclinometer, MatLab, MIDAS, motion control, MSCB, neutrino.

Controlling robots in contact with the environment is an important problem in industry applications. In the conventional force control, much research has paid attention to develop novel force control systems and implemented force sensors to detect external force. This paper shows that narrow bandwidth of force sensor has a big influence on the force control system. Generally, to solve the instability in force control, the velocity feedback gain is enlarged. The system becomes unstable with small velocity feedback gain, and robot's response becomes slow with large one. Inasmuch as there is a tradeoff between the stability and the response, it is considered that force control by robots is difficult. This paper proposes a force control system with disturbance observer. It is possible to obtain the force information with wide bandwidth by using the disturbance observer. This paper shows that bandwidth of force sensing is very important for contact motion control. By using the wide bandwidth of force sensing, both stability and response are improved. Furthermore, force control is attainable by the construction of the easiest force control architecture. Therefore, the ideal zero-stiffness-force control is attained. The numerical and experimental results show viability of the proposed method. Index Terms--Bandwidth, control stiffness, disturbance observer, force control, force sensing, haptics, motion control, robustness.

Kinematic models and motion control algorithms for a two-axle compliant frame mobile robot are examined. General kinematics describing the compliantly coupled nonholonomic kinematics are derived using velocity constraints that minimize traction forces and consider foreshortening of the frame. Given the complexity of these equations, the steering ratio a is defined to describe the relative heading angles of the front and rear axles. Simplified kinematic models are developed based upon a (Types I, II, and III) and the reference point used to guide the robot. Physical limitations and performance metrics (lateral mobility and maneuverability per unit of traction force) are derived to evaluate the models. Six groups of simulations and 24 experimental tests consisting of 120 trials evaluate the performance of the algorithms on carpet, sand, and sand with rocks. Results indicate that Type I (curvature-based steering) provides superior maneuverability and regulation accuracy, whereas Type II provides excellent lateral mobility at the cost of high traction forces, reduced accuracy, and potential singularities. Both models offer significant reductions in complexity for simplified control using standard curvature-based unicycle control algorithms. These results support expectations derived from performance metrics and physical limitations. Experimental results also demonstrate the efficacy of the robot to adapt to and maneuver over extremely rugged rocky terrain. Index Terms--Compliant, kinematics, mobile robot, motion control.

Object-oriented coding in the MPEG-4 standard enables the separate processing of foreground objects and the scene background (sprite). Since the background sprite only has to be sent once, transmission bandwidth can be saved. We have found that the counter-intuitive approach of splitting the background into several independent parts can reduce the overall amount of data. Furthermore, we show that in the general case, the synthesis of a single background sprite is even impossible and that the scene background must be sent as multiple sprites instead. For this reason, we propose an algorithm that provides an optimal partitioning of a video sequence into independent background sprites (a multisprite), resulting in a significant reduction of the involved coding cost. Additionally, our sprite-generation algorithm ensures that the sprite resolution is kept high enough to preserve all details of the input sequence, which is a problem especially during camera zoom-in operations. Even though our sprite generation algorithm creates multiple sprites instead of only a single background sprite, it is fully compatible with the existing MPEG-4 standard. The algorithm has been evaluated with several test sequences, including the well-known Table-tennis and Stefan sequences. The total coding cost for the sprite VOP is reduced by a factor of about 2.6 or even higher, depending on the sequence. Index Terms--Image segmentation, motion analysis, motion compensation, sprite coding, video coding, video signal processing.

In the new video coding standard H.264/AVC, motion estimation (ME) is allowed to search multiple reference frames. Therefore, the required computation is highly increased, and it is in proportion to the number of searched reference frames. However, the reduction in prediction residues is mostly dependent on the nature of sequences, not on the number of searched frames. Sometimes the prediction residues can be greatly reduced, but frequently a lot of computation is wasted without achieving any better coding performance. In this paper, we propose a context-based adaptive method to speed up the multiple reference frames ME. Statistical analysis is first applied to the available information for each macroblock (MB) after intra-prediction and inter-prediction from the previous frame. Context-based adaptive criteria are then derived to determine whether it is necessary to search more reference frames. The reference frame selection criteria are related to selected MB modes, inter-prediction residues, intra-prediction residues, motion vectors of subpartitioned blocks, and quantization parameters. Many available standard video sequences are tested as examples. The simulation results show that the proposed algorithm can maintain competitively the same video quality as exhaustive search of multiple reference frames. Meanwhile, 76%-96% of computation for searching unnecessary reference frames can be avoided. Moreover, our fast reference frame selection is orthogonal to conventional fast block matching algorithms, and they can be easily combined to achieve further efficient implementations. Index Terms--ISO/IEC 14496-10 AVC, ITU-T Rec. H.264, JVT, motion estimation (ME), multiple reference frames.

A motion planning approach to formations of mobile robots with a non-holonomic constraint is presented. The kinematic equations allowed certain class of formations to be maintained while the group as a whole exhibited motion and the method was validated on the Stanford MARS Testbed.

An adaptive backstepping control with friction compensation scheme is presented. A third-order linear dynamic model is used for the ac motor control system design while the LuGre dynamic friction model with nonuniform friction force variations characterizes the friction force. Nonlinear adaptive control laws are designed to compensate the unknown system parameters and disturbances. System robustness and asymptotic position tracking performance are shown through simulation and experimental results. Index Terms--Backstepping control design, motion control, non-linear adaptive control, variation of inertia and load.

In this paper, we show that when it is possible to use feedback in the specification of "motor programs," the length of the descriptions of the instruction sequences for carrying out a given task can be reduced by a factor that reflects the richness of the available feedback signals. The model on which this work is based is that of a finite automaton, modified in such a way that instruction processing is akin to the way in which difference or differential equations "process" piecewise constant inputs. In terms of such "free-running" automata, we show that when feedback is available the length of the shortest description can be reduced by a factor depending on the ratio of the size of the entire state space to the size of the set of states for which feedback is locally effective. Index Terms--Automata, complexity theory, feedback, motion control.

This study develops fuzzy control that is designed with sliding modes to achieve stability of the fuzzy controller. Fuzzy control is formulated in the form of variable structure system (VSS) control. In contrast to previous works in which Lyapunov functions are used to examine the stability, the current study investigates the stability of fuzzy control from the viewpoints of differential geometric methods and the sliding mode theory. Best values for parameters in fuzzy control rules are determined with the aid of sliding modes. In order to improve control performance, a tuning algorithm is executed to adjust parameters for dealing with uncertainties and disturbances. Both computer simulations and experiments with regard to an inverted pendulum hinged to a rotating disk are carried out to validate the proposed method. This apparatus can to some extent represent cornering motion of a motorcycle on which a rider leans to maintain stability. Effects of rider's leaning angle on both stability and handling control are examined according to Bode plots.

A study was conducted to ascertain the effects that carrying a rifle had on the way of walking of an individual. Results revealed that carrying a rifle affected the body's center of mass impeding the arm swing and affected the overall walking style of the individual.

The study presented a concept for integrating the control system of an anthropomorphic robot hand into the control system of an entire humanoid robot. It provided grasp skills to coordinate movements of hand and arm and determines grasp patterns, depending on the object to grasp and the task to execute.

The study revealed that human behaviors consist of both voluntary and involuntary motions. The key idea of the method was to control robots with a hybrid controller that combines the functions of a communication behavior controller and body-balancing controllers. If these controllers had degrees and arrangements of freedom similar to those of humans, the robot's motions would become more natural and human-like.

The attempts to discover the invariant features in a whole-body dynamic task under perturbations are discussed. The features were useful for execution and recognition of a task, and have their origin in human embodiment. The studies stated that a psychological experiment with a unique paradigm was carried out to investigate the relationship of the features to visual recognition of the same motion.

A method for determining load carrying capacity of mobile manipulators with flexible links and joints between two points of their workspace is proposed. It is observed that while the mobile manipulator carries a load along the optimal trajectory, the coupling inertia of the base, links and the load are minimized.

The generalization of a popular motion planning puzzle called Lunar Lockout is computationally intractable is highlighted. The determination of given instance of a generalized lunar Lockout puzzle is solvable is PSPACE-complete is proved and NP-completeness is reviewed.

The solutions to the problem of controlling an anthropomorphic robot arm for personal assistance, by dealing with the peculiarities of its design like the mechanics of its cable-actuated and intrinsically complaint structure are given. The impedance-compliance controller is more appropriate to the given application as well as to the peculiar cable-actuated structure.

A multisine approach for dmotion control , which is based on information gain, of a robot moving between two configurations is presented. The effectiveness of the approach is shown by different simulation results with a wheeled mobile robot (WMR) in an environment with and without obstacles.

A distributed smooth time-varying feedback control law that asymptotically stabilizes multiple nonholonomic mobile robots of the Hilare-type to capture/enclose a target by making troop formations is presented. This robotic system is a hybrid system that consists of smooth time-varying feed-back control and a reactive control framework and its validity is supported by computer simulations.

An asymptotic control with driftless constraints is proposed for wheeled mobile robots with the convergence proof by using Lyapunov stability theory. Findings show that the behavior of the motion controller asymptotically converges to the reference trajectory and in the numerical simulation, the performance of the asymptotic control is effective without zigzag movement in both ideal and nonideal velocity controllers for two driving wheels with the appropriate selection of control parameters.

A novel three degrees of freedom (DoFs), that are two degrees of translational freedom and one degree of rotational freedom, parallel robot is proposed. Results show that the solution of inverse kinematics can reach eight and the solution of forward kinematics can be four and the velocity equation of the new parallel manipulator is given.

A Nitinol artificial muscle stress-strain-power relationship is determined by experimentation and a simple mathematical model is developed based upon the experimental results. Findings show that the simulation results for the height postures are in agreement with the actual height values and that the weight-buoyancy couple has a stabilizing effect on the vehicle, which reduces the actual pitch and roll angles that can be obtained.

A dynamic modeling technique for a manipulator with multiple flexible links and flexible joints, based on a combined Euler-Lagrange formulation and assumed modes method is presented. Findings show that with application of the proposed controller to a flexible link and flexible joint manipulator, good tracking is performed and both link and joint vibrations are suppressed effectively.

The position control problem of a two-degree-of-freedom manipulator with a flexible second link and artificial muscle-type pneumatic actuators is investigated both theoretically and experimentally. The simulations and the experimental results show that the proposed composite control scheme produces good position tracking performances and guarantees the stability robustness against various uncertainties, especially under plus-minus 30% payload variations.