Showing papers by "Keigo Watanabe published in 2010"

Noncontact position estimation device with optical sensor and laser sources for mobile robots traversing slippery terrains

Abstract: This paper describes the development of a sensing device that can be used to estimate the position of mobile robots on slippery terrains. The device consists of an optical sensor designed for a computer mouse and dual laser light sources for generating a laser speckle pattern. It detects the motion of a moving surface at a large distance from the surface, from 80 mm to 300 mm, by tracking the laser speckle pattern. The use of dual laser light sources makes the tracking robust for both large distances from the ground and different surface materials. Some fundamental experiments validated the performance of the device, which tracked surfaces of different materials with high accuracy under various height conditions. Finally, the device was mounted on our mobile robot, and simple experiments were conducted on a slippery sandy terrain to evaluate the usefulness of the device as a noncontact odometry system.

Underactuated control for nonholonomic mobile robots by using double integrator model and invariant manifold theory

Abstract: In a stabilizing control for nonholonomic mobile robots with two independent driving wheels, a nonholonomic double integrator in the kinematic model is first considered as a controlled object model. Then, a quasi-continuous exponential stabilizing control method is proposed as one of underactuated control methods by using invariant manifold theory. Next, to extend the velocity input control in a kinematic level to the torque input control in a dynamical level, an extended nonholonomic double integrator consisting of the kinematic and dynamical models is treated as a controlled object model. A quasi-continuous exponential stabilizing controller is further derived for such an extended model by using the same way as used in the kinematic level control. The effectiveness of the present method is proved with some demonstrative simulations.

Interpretation of fuzzy voice commands for robots based on vocal cues guided by user's willingness

Abstract: This paper proposes a method for interpretation of fuzzy voice commands based on the vocal cues. The fuzzy voice commands include fuzzy linguistic terms like “little” and quantitative meaning of such terms depends on the environmental conditions. Therefore the robot's perception of the corresponding environment is modified by acquiring the user's perception through a series of vocal cues. The user's willingness to change the robot's perception is identified based on the vocal cues to improve the adaptation process. The primitive behaviors related to the end-effector movements of a robot manipulator are considered and evaluated by a behavior evaluation network (BEN). A vocal cue evaluation system (VCES) is used to evaluate the vocal cues to adapt the robot's perception by modifying the BEN. The user's satisfactory level for the robot's movements is utilized to track the satisfaction of the user. A situation of cooperative rearrangement of the user's working space is used to illustrate the proposed system by a PA-10 robot manipulator.

Switching manifold control for an extended nonholonomic double integrator

Abstract: Control approaches for nonholonomic systems have utilized canonical forms A nonholonomic double integrator model is the one of canonical forms for nonholonomic systems Outputs of the controller based on the nonholonomic double integrator model are velocity commands for the kinematic model of a nonholonomic system In this paper, we consider an extended nonholonomic double integrator model, in which control inputs are torque or force commands We propose a switching controller based on the invariant manifold theory Each controller is designed with a quasi-continuous exponential stabilized control The effectiveness of the present method is verified by some simulations

Interpreting Fuzzy Linguistic Information by Acquiring Robot's Experience Based on Internal Rehearsal

Abstract: This paper proposes a method for interpreting fuzzy linguistic information by acquiring robot's experience on previous movements. The quantitative assessment for a fuzzy linguistic term such as “little” depends on the spatial arrangement of surrounding environment. Robot's experience on previous movements is very useful for understanding such information in a context dependant manner. Therefore, an internal rehearsal system is introduced to acquire the robot's experience on previous movements. Such acquisition enhances the robot's capability to interpret fuzzy linguistic information in fuzzy voice commands (FVCs) according to the current environmental context. The proposed system is used to evaluate the fuzzy linguistic information related to primitive movements of a robot manipulator. Those primitive movements are realized by a behavior evaluation network (BEN) with the guidance of an internal rehearsal system. The end-effector movements and the single joint movements of a robot manipulator are considered as primitive movements. They are activated by fuzzy voice motion commands (FVMCs) and fuzzy voice joint commands (FVJCs) respectively. The proposed idea is demonstrated with a PA-10 robot manipulator by navigating the robot manipulator in the user's working space. The use of the behavior evaluation network and the internal rehearsal system introduced a better way of assessing fuzzy linguistic information by acquiring the robot's experience on the corresponding environment.

A switching control method for stabilizing a nonholonomic mobile robot using invariant manifold method

Abstract: A system with nonholonomic constraints attracts its attention from the viewpoint of control theory because any conventional control cannot be applied directly to such a system. Since it cannot be stabilized by a static continuous feedback with constant gains, there are several control methods up to now by using a chained form etc. Among them, a switching control method using invariant manifold, which is considered as a generalized form for sliding mode control known as one of conventional switching control methods, and a quasi-continuous exponential stabilizing control method are proposed in a power form system with two inputs and three states or two inputs and n-states. In this study, as a new mehod, a switching control method using an invariant manifold as mentioned above is examined for a “double integrator system,” known as an alternative canonical model for nonholonomic systems. In particular, stabilizing controllers are derived for the case of a kinematic model with two inputs and three states and for the case of a dynamic model with two inputs and five states, which is just as an “extended double integrator system.” The effectiveness of the proposed controllers is demonstrated through simulations for a mobile robot with two independent driving wheels.

Adaptation of robot's perception of fuzzy linguistic information by evaluating vocal cues for controlling a robot manipulator

Abstract: This article proposes a method for adapting a robot's perception of fuzzy linguistic information by evaluating vocal cues. The robot's perception of fuzzy linguistic information such as "very little" depends on the environmental arrangements and the user's expectations. Therefore, the robot's perception of the corresponding environment is modified by acquiring the user's perception through vocal cues. Fuzzy linguistic information related to primitive movements is evaluated by a behavior evaluation network (BEN). A vocal cue evaluation system (VCES) is used to evaluate the vocal cues for modifying the BEN. The user's satisfactory level for the robot's movements and the user's willingness to change the robot's perception are identified based on a series of vocal cues to improve the adaptation process. A situation of cooperative rearrangement of the user's working space is used to illustrate the proposed system by a PA-10 robot manipulator.

Desktop orthogonal-type robot with abilities of compliant motion and stick-slip motion for lapping of LED lens molds

Abstract: In this paper, a new desktop orthogonal-type robot, which has abilities of compliant motion and stick-slip motion, is first presented for lapping small metallic molds with curved surface. The robot consists of three single-axis devices with a high position resolution of 1µ. A thin wood stick tool is attached to the tip of the z-axis. The tool tip has a small ball-end shape. The control system is composed of a force feedback loop, position feedback loop and position feedforward loop. The force feedback loop controls the polishing force consisting of tool contact force and kinetic friction forces. The position feedback loop controls the position in pick feed direction, e.g., z-direction. The position feedforward loop leads the tool tip along a desired trajectory called cutter location data (CL data). The CL data are generated from the main-processor of a CAM system. The proposed robot realizes a compliant motion required for the surface following control along a spiral path. In order to improve the lapping performance, a small stick-slip motion control strategy is further added to the control system. The small stick-slip motion is orthogonally generated to the direction of the tool moving direction. Generally, the stick-slip motion is an undesirable phenomenon and should be eliminated in precision machineries. However, the proposed robot employs a small stick-slip motion to improve the lapping quality. The effectiveness of the robot is examined through an actual lapping test of an LED lens mold with a diameter of 4 mm.

An unscented Rauch-Tung-Striebel smoother for a bearing only tracking problem

Abstract: The unscented Kalman filter (UKF) has become a new technique used in a number of nonlinear estimation problems to overcome the limitation of Taylor series linearization. It uses a deterministic sampling approach known as sigma points to propagate nonlinear systems and has been discussed in many literature. However, a nonlinear smoothing problem has received less attention than the filtering problem. Therefore, in this article we examine an unscented smoother based on Rauch-Tung-Striebel form for discrete-time dynamic systems. This smoother has advantages available in unscented transformation over approximation by Taylor expansion as well as its benefit in derivative free. To evaluate the performance of this smoother, we compare this algorithm with an extended Rauch-Tung-Striebel algorithm through the simulations of a bearing-only tracking problem.

CAD/CAM-based force controller using a neural network-based effective stiffness estimator

Abstract: In industries manufacturing metallic molds, various NC machine tools are used. We have already proposed a desktop NC machine tool with compliance control capability to automatically cope with the finishing process of LED lens molds. The NC machine tool has the ability to control the polishing force acting between an abrasive tool and a work piece. The force control method is called impedance model force control. The most effective gain is the desired damping of the impedance model. Ideally, the desired damping is calculated from the critical damping condition after considering the effective stiffness in the force control system. However, there is a problem in that the effective stiffness of the NC machine tool has undesirable nonlinearity. The nonlinearity has a bad influence on the force control stability. In this article, a fine tuning method of the desired damping is considered using neural networks. The neural networks acquire the nonlinearity of effective stiffness. The promise is evaluated through an experiment.

A formation method for heterogeneous multiple robots by specifying the relative position of each robot

Abstract: In this paper, we propose a formation method that can specify the position of each robot in a group. The robots are assumed to be heterogeneous and identified. Also assume that a formation is composed of some equilateral triangles. The method is verified through some simulations. When applying the method to a real robot system, it needs to obtain IDs and relative positions of the robots. We further propose the measurement system using wireless communication and ultrasonic sound. Such a system is evaluated in the estimation accuracy of relative positions through some experiments in a simulated environment.

Visual evaluation and fuzzy voice commands for controlling a robot manipulator

Abstract: This paper proposes a method for learning and controlling an industrial robot manipulator through Fuzzy Voice Commands (FVCs) guided by visual motor coordination. Supervised Self-Organising Map (SSOM) is proposed to implement the visual motor coordination. The FVCs are used to control the robot manipulator toward a goal. Visual evaluation process is adapted by the supervision of the human coach. The learned system is capable of navigating the robot manipulator to a point in 3D working space as instructed by the voice commands. The proposed idea is demonstrated with a PA-10 industrial manipulator.

Navigation strategy for a quadruped robot on soft flat ground

Abstract: Tasks important for a mobile robot are the environmental recognition and the obstacle avoidance in the real world. The legged robot can be adapted for rough terrains. It is because the legged robot has a high degree of freedom in order to avoid an obstacle to three dimensions. In this paper, we propose a locomotion strategy on the terrain with stiffness which is different in each. The propriety of a continuation walk is determined by the force sensor mounted to the bottom of each leg of a quadruped robot. The effectiveness of the proposal approach is verified from the result of the experiment which uses the prevalent quadruped robot called TITAN-VIII.

Skillful stick-slip motion control of a Cartesian-type robot

Abstract: Friction known as friction heat, friction noise, friction wear and friction force and so on is an undesirable physical phenomenon in almost all machine systems In this paper, however, a friction force generated by a stick-slip motion is introduced to improve the lapping quality of small LED lens molds Here, the lapping means the finishing or polishing of metallic molds by using diamond paste A novel desktop Cartesian-type robot, which has abilities of compliant motion and stick-slip motion, is first presented for lapping small metallic molds with a curved surface such as an LED lens mold The robot consists of three single-axis devices with a high position resolution of 1 µm built in Cartesian-space A thin wood stick tool is attached to the tip of the z-axis The tool tip has a small ball-end shape with a diameter of 1 mm The control system is composed of a force feedback loop, position feedback loop and position feedforward loop The force feedback loop controls the polishing force consisting of contact force in normal direction and kinetic friction forces in tangent direction It is assumed that the kinetic friction forces are generated by Coulomb friction and viscous friction In order to improve the lapping performance, a stick-slip motion control method is further added to the control system The small stick-slip motion is orthogonally generated to the tool moving direction, so that the polishing energy can be finely changed to partially improve the lapping quality The effectiveness is examined through an actual lapping test of an LED lens mould with a diameter of 4 mm

Attentive and corrective feedback for adapting robot's perception on fuzzy linguistic information

Abstract: This paper proposes a method for understanding the fuzzy linguistic information based on the user's guidance. A quantitative assessment for a fuzzy linguistic term such as “little” depends on the environmental conditions. Therefore the corrective feedbacks are utilized to adapt the robot's perception toward the corresponding environment. However, the attentive commands like “move carefully” are used to modify the evaluation process of the fuzzy linguistic information according to the user's desire. The primitive behaviors are evaluated by a behavior evaluation network (BEN) and a feedback evaluation system (FES) is utilized to evaluate the corrective feedbacks. An attention level controller is introduced to change the attention level based on the attentive commands. The system is adapted toward the user's perception on the fuzzy linguistic information based on the corrective feedbacks in the adaptation phase. Then the attentive commands are used to modify the evaluation process according to the local requirements. The proposed system is demonstrated by using a PA-10 robot manipulator and a situation of cooperative rearrangement of user's working space is considered. The adaptation of the system toward the environmental conditions by the corrective feedbacks and the capability to use the attentive feedbacks to modify the system during the work, improve the effectiveness of the system.

An Image-based Method for Controlling the Trajectory Tracking of Mobile Robots

Abstract: Kurashiki et al. have already studied an imagebased robust trajectory tracking control for a nonholonomic mobile robot. In particular, they considered a situation when the trajectory line and the image plane satisfy a constrained condition. However, it should be noted that in a practical case, there is an alternative situation, which is just as a complimentary case of that studied by Kurashiki et al. Thus, the present image-based method completes the trajectory tracking control for nonhonolomic mobile robots, in which the objective of the trajectory tracking is set as a line tracking in a two-dimensional image plane. The effectiveness of the present method is illustrated through a simulation.

Stick-slip motion control based on cutter location data for an orthogonal-type robot

Abstract: In this article, a new desktop orthogonal-type robot, which has the capacity of stick-slip motion control based on cutter location data, is presented for lapping small metallic molds with a curved surface. The robot consists of three single-axis devices with a high position resolution of 1 μm. A thin wooden stick tool with a ball-end shape is attached to the tip of the z-axis. In order to improve the lapping performance, a novel stick-slip motion control method is developed in the control system. The small stick-slip motion is orthogonally generated in the direction of the tool's movement. The effectiveness of stick-slip motion control is examined through an actual lapping test of an LED lens cavity.

Compliance model following force control for open-architectural industrial robots

Abstract: This paper presents a compliance model following force control that can take account of a desired position in the force control, and gives a transformation technique from the position command to the torque command in order to apply the controller to an industrial robot, whose servo system is technically opened, or to implement it in computer simulations. Next, to determine a suitable compliance without trial and error, a method that produces desired time-varying damping for critical damping is introduced by using the information on inertia and Jacobian. Simulation results using a dynamic model of an industrial robot PUMA560 have shown that the proposed methods are effective for realizing the controller in the robot, and for improving the force control performance.

Desktop Cartesian-Type Robot with Abilities of Compliant Motion and Stick-Slip Motion

Abstract: In manufacturing process of small lens molds, 3D CAD/CAM systems and high precision NC (numerically controlled) machining centers are used generally, and these advanced systems have drastically rationalized the design and manufacturing process. For example, recently, an ultra precision multi-axis control machining system has been developed for spherical micro-lens array molds. As a result, the mold with a spherical micro lens array has been effectively shaped with high accuracy (Oba et al., 2008). In case of an LED lens mold as shown in Fig. 1, however, the finishing process after the machining process has been hardly automated yet, because the LED lens mold has plural small concave areas to be finished, in which each diameter is 4 mm.

Position-based impedance control using inner servo system and its application to a desktop NC machine tool

Abstract: A position-based impedance control using an inner servo system is introduced for industrial manipulators. Stiffness control, compliance control and impedance control can be easily realised. The impedance control does not have a force control mode but is the combination of position, velocity and force. The proposed impedance model force control is derived from the concept of the position-based impedance control. The force control method is applied to an NC machine tool to have a compliance. The machine tool consists of three single-axis robots with a high position resolution of 1 µm. The basic performance is demonstrated through a profiling control experiment.

2A2-D30 Robust Positioning Device with Optical Sensor and Dual Laser Sources for Mobile Robots Traversing Slippery Terrains

Abstract: This paper describes the development of a sensing device that can be used to estimate the position of mobile robots on slippery terrains. The device consists of an optical sensor designed for a computer mouse and dual laser light sources for generating a laser speckle pattern. It detects the motion of a moving surface at a large distance from the surface, from 80 mm to 300 mm, by tracking the laser speckle pattern. The use of dual laser light sources makes the tracking robust for large distances from the ground. Some fundamental experiments validated the performance of the device, which tracked surfaces with high accuracy under various height conditions. Finally, the device was mounted on our mobile robot, and simple experiments were conducted on a slippery sandy terrain to evaluate the usefulness of the device as a noncontact odometry system.