Nobuaki Takanashi

A high-sample-rate robot control system using a DSP based numerical calculation engine

A high-sample-rate robot controller has been designed to resolve computational requirements in advanced algorithms, such as the computed torque method or various impedance control algorithms. An active stiffness control algorithm for a six-degree-of-freedom manipulation has been implemented on the controller, and a 1 kHz sampling rate has been achieved. The design assumes no specific algorithm and robot configuration, and it is easy to increase the number of drive joints. The controller is equipped with a general-purpose vector/matrix calculation engine, servo drivers, and a 16-bit microcomputer system. The calculation engine, which accelerates hole computation for advanced control methods, is based on a 13.4 MFLOPS single-chip floating-point digital signal processor (DSP). This engine was developed to simplify DSP programming without degrading its high-performance computation capabilities. Basic vector/matrix functions and general functions for scalar value computation are mask ROMed on the DSP chip. The controller construction and calculation engine functions, and their performance, are addressed.<<ETX>>

A 470 × 235-ppi poly-Si TFT-LCD for high-resolution 2-D and 3-D autostereoscopic displays

— We have developed a 470 × 235-ppi poly-Si TFT-LCD with a novel pixel arrangement, called HDDP (horizontally double-density pixels), for high-resolution 2-D and 3-D autostereoscopic displays. 3-D image quality is especially high in a lenticular-lens-equipped 3-D mode because both the horizontal and vertical resolutions are high, and because these resolutions are equal. 3-D and 2-D images can be displayed simultaneously in the same picture. In addition, 3-D images can be displayed anywhere and 2-D characters can be made to appear at different depths with perfect legibility. No switching of 2-D/3-D modes is necessary, and the designs thin and uncomplicated structure makes it especially suitable for mobile terminals.

Dual-lenticular-lens-based 2-D/3-D convertible autostereoscopic display

— A 2-D/3-D convertible display using two lenticular lenses has been developed. It shows 2-D pictures in full resolution and 3-D autostereoscopic pictures in half resolution by moving one lens relative to the other. The lens assembly consists of thin metal frames, two lenticular lenses, and two shape-memory-alloy (SMA) wires used as actuators. While this assembly is applicable to flat-panel displays of any kind, its simple structure and low power consumption make it best suited to mobile terminals, such as PDAs and mobile phones. Here, we describe its structure and present evaluation results.

A Telerobot System For Space Antenna Assembly Experiments

This paper describes a telerobot system and its application to space antenna assembly experiments. In this system, the operator utilizes an Integrated Teleoperation Console to operate multiple arms and cameras from a remote site, employing such system supports as visual guidance, ForcelTorque sensing, interactive user interface, and real-time graphic kzsk simulation. Visual guidance is semi-autonomous in that the robot itself is also capable of interpreting visual information and grasping target objects. In the study, assemblyldisassembly experiments are carried out on an space antenna consisting of a center dish surrounded by eight separate outer antenna segments. The accuracy of visual guidance positioning is evaluated experimentally. Results prove the effectiveness of both the telerobot experiment system and the space antenna structure. investigate this systems potential effectiveness for use in space. The antenna used was a version with improved assembly reliability. The positioning accuracy of the semi- autonomous visual guidance system was first evaluated experimentally, and then multiple segments were assembled and disassembled. In the segment grasping stage of the assembly experiments, the segment holder position was shifted to verify visual guidance. Positioning shifts were intentionally applied to robot motion commands in the assembly stage of the experiments to simulate actual robot motion in space. In spite of these shifts, accurate coupling was successfully achieved and the effectiveness of the system demonstrated.

A prototype space telerobotic system

Describes an antenna assembly robot system. The system is composed of a teleoperating console, a real-time simulator, a robot arm, a robot controller and an assembly model space antenna. The console is equipped with a vision sensor using target marks to guide the antenna segment. The target mark image is superimposed with the reference target mark figure, so relative position differences from a desired object position can be detected visually. The real-time robot simulator is used to check the robot motion during the teleoperation. Antenna assembly experiments were carried out to investigate the effectiveness of using this system. Also, the vision sensor position detection accuracy was evaluated experimentally. To reduce operators burdens, another target mark for a visual feedback was designed and a two-arm telerobotic system, which includes a vision arm and a working arm, was proposed. Measurement accuracy of the vision sensor using the mark was also evaluated by numerical simulation. Using these space telerobotic systems, an astronaut can accomplish the task, such as the antenna assembly, without human extravehicular activities.<<ETX>>

6 DOF manipulators absolute positioning accuracy improvement using a neural-network

An absolute positioning accuracy improvement method, using an artificial neural network, has been developed. In this method, an artificial neural network is used with a conventional inverse kinematics computation module in parallel. The network automatically learns the manipulator model errors. When a manipulator carries out tasks, both the network and the inverse kinematics computation module receive the commanded end effector location, described in a Cartesian coordinates. The network output is summed together with the inverse kinematics computation module output in a joint coordinate. Driving the manipulator joint by summed result, manipulator endpoint positioning accuracy is improved. The effectiveness of this method was investigated experimentally by using a 6 DOF (degrees-of-freedom) manipulator forward kinematic model with model error. Results show that the absolute positioning error has been reduced by 1/3. Also this method was effective in a work area which was not used for the network learning.<<ETX>>

39.4: A Metal-Based High-Resonant-Frequency Optical Scanner with a Moving-Magnet Actuator for Non-Resonant Large-Angle Scanning

A metal based optical scanner for non-resonant drive has been developed. A thin magnet, installed beneath a scan mirror, drives the mirror over +/−20 degrees of optical angle. The moving magnet actuators large torque enables designing the torsion spring constant high for high resonant frequency, which makes laser projectors bright and optically efficient.