DEVELOPMENT OF THE HUMANOID ROBOT HUBO-FX-1

Transcription

1 DEVELOPMENT OF THE HUMANOID ROBOT HUBO-FX-1 Jungho Lee, KAIST, Republic of Korea, Jung-Yup Kim, KAIST, Republic of Korea, Ill-Woo Park, KAIST, Republic of Korea, Baek-Kyu Cho, KAIST, Republic of Korea, Min-Su Kim, KAIST, Republic of Korea, In-Hyuck Kim, KAIST, Republic of Korea, Jun-Ho Oh, KAIST, Republic of Korea, ABSTRACT We developed human like biped robot, HUBO FX-1, which can carry human or luggage. Its height is 1.393m and weight is 130Kg and it can stand maximum 100Kg payload. It can be controlled by wireless network or joystick and all electrical parts are installed inside. It can rotate and move forward and backward with maximum 1.25Km/h speed. Also we probe robustness of walking algorithm which is used former HUBO series. KEYWORD : HUBO, KHR, Humanoid, Biped robot, Biped locomotion, Robot 1. INTRODUCTION Recent research about human like biped robot is developed based on mechanical engineering, electrical engineering, computer science and so on. Human like biped robots which are developed recently can walk up-stairs and even more run[4][5]. However there are a few research papers about practical use of Human like biped robots. HUBO FX-1 is developed for carrying human or luggage. This is very useful to industry like construction and to entertainment industry. Because HUBO FX-1 use two leg as transportation method, it can make up for the weak points in wheel and caterpillar. This paper consist 3 main paragraphs. First paragraph explain about mechanical design to carry human or maximum 100Kg payload. Second paragraph explain what kind of controllers and electrical parts are used to realize stable walking algorithm. And last paragraph explain conclusions. 2. MECHANICAL DESIGN 2.1 Overview HUBO FX-1 has 12 DOF include 2 DOF in ankle, 1 DOF in knee and 3 DOF in hip each

2 leg and is biped robot which can carry up to 100Kg payload. Figure 2-1 shows HUBO FX-1 with a seat for carrying human. And it can be changed other type carrier on their own purpose. Except its upper body, the height of HUBO FX-1 is 1.393m and its weight is about 130Kg. And also it can walk 1.25Km/h. All of the main controller and other devices are embedded in the robot. So, operators can control HUBO FX-1 through wireless network and a joystick. We applied former HUBO s walking algorithm and also verified the algorithm is very stable. Table 2-1 shows overall specifications of HUBO FX-1. Figure 2-1 HUBO FX-1 Research Term ~ Height and Weight 1.393m(1.988 with chair) and 130Kg(150Kg with chair) Walking Speed 1.25Km/h Actuator AC Servo motor + Harmonic Reduction Gear + Drive Unit Control Unit Main controller, sub-controller and AC servo controller Sensor Foot 3-Axis Force-Torque Sensor and Inclinometer Torso Rate-Gyro and Inclinometer Power External AC power(220v) Operation Windows XP and RTX with Wireless network and joystick DOF 12 DOF Table 2-1 Specification of HUBO FX Mechanical Design The main principles of mechanical design in HUBO- FX-1 are to get very simple structure so as to make mathematics and manufacturing easy ant to have enough stiffness to stand maximum 100Kg payload. To make simple structure, we make all joint axes to meet in one single point and all parts are based on 2 dimensional machining. So hip joint looks like a ball joint and ankle joint looks like universal joint[1]. To stand maximum 100Kg payload we

3 minimized own weight and designed to have enough stiffness. In figure 2-2, to obtain this, we minimized thickness and also added horizontal plate to stand torsion due to payload. Also we designed additional parts to prevent bearings in hip and ankle joint come out due to oscillation in lower body which is caused by roll moment(figure 2-3). Overall mechanical dimension is based on human and operating range of each joint is shown by Table 2-2. Figure 2-2 mechanical design of HUBO FX-1 Figure 2-3 Additional parts for hip and ankle joint Hip Ankle Joint Operating range(degrees) Yaw -77 to +60 Pitch -90 to 90 Roll -90 to +38 Pitch -90 to 90 Roll -40 to +20 Knee 0 to 150 Table 2-2 Operating range of each joint 2.2 Actuators and Reduction gears AC servo motor is used for actuating HUBO-FX-1 joints. Because general motor which is

4 used for general biped robot cannot be sufficient needed design parameters. Each motor and reduction gear for joints is selected using computer simulation to withstand self weight and maximum 100Kg payload. Also to minimize backlash phenomenon, we use Harmonic Drive System each joint and it is connected to the motor by pulley-belt system. Table 2-3 dedicate AC motor, Harmonic Drive System. AC servo motor Harmonic Drive System 1.27 Nm 400Watt Inertia 0.34 gf cm s 2 RPM 5000 rpm 2.39 Nm 800Watt Inertia 1.08 gf cm s 2 RPM 5000 rpm CSF-25 Reduction ratio 100:1 108 Nm CSF-32 Reduction ratio 100:1 212 Nm Table 2-3 Actuators and reduction gears 3. ELECTRICAL DESIGN 3.1 Overview Electrical parts of HUBO FX-1 are different from the former HUBO series. Because HUBO FX-1 uses AC servo motors, former HUBO series use small DC motors, there are additional electrical devices. Figure 3-1 dedicates overall structure of the system. Main controller(rtx, Stable walking..) Sub controller(dsp, CAN..) Sensoes AC servo controller Motor Figure 3-1 Overview of control system We use the Windows XP as main operating system and also use the RTX for real time control. Controllers are made up of main controller, sub-controller and AC servo controller and sensors are made up of 3-axis force-torque sensor, rate gyro sensor and inclinometer. Sensors are communicated with main controller using CAN communication protocol.

5 3.2 Controller Controllers are made up of main controller, sub-controller and AC servo controller. The main controller has the PCI bus type sub-controller that the former HUBO series don t have. The main controller conducts control algorithm using sensor signals and offers reference position information for each motor to the sub-controller during 0.01ms time period. The subcontroller offers reference position and direction signal for each motor with 50KHz, which are created by DDA(Digital Differential Analysis) algorithm, to the AC servo controller base on this information(figure 3-2). Figure 3-2 Diagram of sub-controller Using this procedure AC servo controller controls each motor. Figure 3-3 dedicates timing diagram of the sub-controller. PLX set RQ signal to high so inform to DSP that data is valid. Then the DSP get each data and return RT signal to inform acknowledgement to the PLX. This procedure is conducted twelve times per 10msec and all information needed to control motor are transmitted to DSP. The sub-controller has a CAN communication module and it is used for communicating with sensors. SJA1000 is a stand-alone CAN controller manufactured by Philips which has inner Rx/Tx buffers, Bit Stream Processor and Acceptance Filter. It supports CAN 2.0B protocol and has maximum 1Mbps communication speed. PCA82C250 as CAN transceiver has 1Mbaud rate and maximum 50nsec propagation delay. Figure 3-3 Timing diagram of sub-controller

6 Also we use AC servo motor driver named CSDJ servo controller series developed by Samsung Electronics and Table 3-1 shows servo controller s specifications. Power Control Method Control Mode Encoder Input Impedance Circuit time constant AC 220V(50-60Hz) Single phase PWM control using IPM with 32bit High speed DSP 7 Modes include Position, Velocity and Torque Control Mode 2048 PPR incremental type(a, B and Z phase) 50KOhm 35 us Table 3-1 AC servo controller 3.3 Sensors 3-axis force-torque sensor, rate gyro sensor and inclinometer are used for HUBO FX-1. Figure 3-4 dedicates 3-axis force-torque sensor structure and controller installed in each foot. It can measure 1-axis force and 2-axis moment and has auto-balancing and auto nulling point control using the controller. Figure 3-4 Force-Torque sensor module Inclinometer sensor installed in each foot is used to measure slope of ground(figure 3-5)[2][3]. It uses ADXL203 accelerometer manufactured by Analog Device and can measure a slope of ±15 degrees. In torso, there are rate gyro sensor and inclinometer. The rate gyro sensor is a CRS03 manufactured by Silicon Sensing and inclinometer is a DM1 manufactured by DAS(Digital Advanced Sensor). Table 3-2 dedicates specifications of the sensor. Figure 3-5 Inclinometer for foot Figure 3-6 Rate-Gyro and inclinometer

7 Rate gyro sensor (CRS03) Inclinometer (DM1) Measuring range ± 100 degrees/s Bandwidth 10 Hz Drift vs. time <±0.05degree/s in any 30s Non-linearity < 0.5 % FS Measuring range ±15 degrees Response time < 0.3 s Temp. drift 0.12 %/K Non-linearity < 0.2 % FS Table 3-2 Specifications of sensors 4. CONCLUSIONS In this research we concluded : i. We designed mechanical parts for carrying human and to stand maximum 100Kg payload. ii. We designed electrical parts such as controllers, 3-axis force-torque sensor and inclinometers. iii. We apply robust walking algorithm which is developed for HUBO series. 5. ACKNOWLEDGEMENTS i. This project is sponsored by MOCIE(Ministry Of Commerce, Industry and Energy). ii. HUBO FX-1 is demonstrated at the APEC 05(Asia-Pacific Economic Cooperation). 6. REFERENCES [1] Jung-Yup Kim, Ill-Woo Park, Jungho Lee, Min-Su Kim, Baek-kyu Cho and Jun-Ho Oh, System Design and Dynamic Walking of Humanoid Robot KHR-2, IEEE International Conference on Robotics & Automation, 2005 [2] Jung-Yup Kim, Seo-Wook Park, Ill-Woo Park and Jun-Ho Oh, "Design and walking control of the humanoid robot KHR-2(KAIST Humanoid robot-2)", ICCAS 2004 [3] Ill-Woo Park, Jung-Yup Kim, Seo-Wook Park, and Jun-Ho Oh, "Development of Humanoid Robot Platform KHR-2(KAIST Humanoid Robot-2)", Humanoid [4] Jung-Hoon Kim and Jun-Ho Oh, "Realization of dynamic walking for the humanoid robot platform KHR-1", Advanced Robotics, 2004 [5] Jung-Hoon Kim, Jun-Ho Oh, "Walking Control of the Hummanoid Platform KHR-1 based on Torque Feedback Control" Proc. of IEEE International Conference on Robotics and Automation, 2004