Southern Taiwan University Mechanical Engineering Department SILO4 Walking Robot Course: Robotic...
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Southern Taiwan UniversityMechanical Engineering DepartmentSILO4 Walking Robot Course: Robotic Teacher: Wu. Min- Kuang Student: Phan. Quy- Phai Student number: M961Y211Taiwan, January 2008Presentation
Out lineIntroduction.Main characteristic .Robot configuration.Body structure.Leg configuration.Food design.Some insights parts developed . + System Configuration.+ Computing system. + Sensors and sensor system.+ Control algorithms.Summary.References.
Introduction During the last three decades, walking machine technology has been exciting field of investigation for robotic, and many improvements have been developed since then first computer-controller prototypes of the early 1970s. Since then, a large number of walking robots has been developed all over the word. One of the walking robots is SILO4 walking robot. The SILO4 walking robot is a medium-sized quadruped mechanism built for basic research and development as well as for educational purposes. The SILO4 is a compact, modular, robust machine cable of negotiating irregular terrain, surmounting obstacles up to 250 mm tall and carrying about 15kg in payload at a maximum velocity of about 1.5 m/min, depending on the gait it is using. The SILO4 has proven very efficient in research on motion generation, terrain adaptation, stability analysis, e.t.c. And it is expected to be the same in subjects such as artificial intelligence, perception integration, teleoperation and so on. This robot can work in an outdoor environment under non extreme conditions.
Main characteristic. Four legs Small size and low weight for easy handing.Mechanical robustness.Slenderness, so as to avoid motor position that give big leg volumes.Compactness, with all motors and electrical cables conveniently housed.Agility in changing trajectories for good omnidirectionalityControl provided by a true real-time multitasking operating system supporting network communication
Robot configurationThe SILO4s legs are placed around the body in a circular configuration. In astatically stable, the configuration is distributed symmetrically about longitudinal and transversal body axes are distributed symmetrical.The place along the sides of legs is parallel to the longitudinal.
The body of the robot is similar to a parallelepiped measuring about 310 x 310 x 300 mm.
it contains all of the drivers and electronic card.
It is made of aluminum, bodys weight is about 18 kg.
The upper part of body installs auxiliary equipment and exteroceptive sensors.
The four side walls also can be used for the same above purposes.
The legs of the robot are based on an insect-type configuration.
The leg parts are mainly manufactured in aluminum, and some specific parts are made of aluminum 7075T6.
The second and third joints axes lie parallel to each other and perpendicular to the axis of the fist joint.
The first link is about 60 mm long, and the second and third links are about 240mm.
Each joint is actuated by a dc servomotor, the motor are embedded in the leg structure.
The motor are provided with planetary gear.
Leg configuration (continue)The output shaft of a planetary drives the first joint.The second and third joints have an additional reducer based on a skew - axis spiroid mechanical.Spiroid gear consist of a tapered pinion, which resembles a worm, and a face gear with teeth curved in a lengthwise direction.
This is table summarizes the main characteristics of the leg joints
Food designThe normal SILO4 foot consists of a passive universal joint. A three axis piezoelectric force sensor placed in the third link above passive joints.A simpler articulated foot without a force sensor and half-sphere foot with a passive joint. [see Fig 4(b) and 4(c), respectively ]
This is summarizes the main features of the SIL04 walking robot.
The overall SILO4 system admits two different configuration.
+ The first configuration consists of : a unique computer on board the robot, a dc power supply provides power to computer and robot motors, a screen and keyboard.
+ The second configuration consists of: two computer ( the controller runs on the onboard computer), a batteries, radios.
The control system, is a distribute hierarchical system compose of a PC-based computer, a data-acquisition board, and four three-axis control board based on the LM 629 microcontroller, interconnected through an industry standard architecture (ISA) bus.
The LM629 microcontroller include digital proportional-integral-derivative (PID).
Every controller has a dc motor joint driver based.
Additional component could be added depending on the sensor used in the system
Sensors and sensor systemThe robot possess internal sensors, and it uses an encoder on each joint as a position sensors.
The robot can include different sensors depending on the foot type: +if the robot has articulate feet with force sensors then the sensor system will possess a three-axis force sensor and two potentiometers per foot. + if the robot is articulate with no force sensors then the sensor system will incorporate an on/off switch on each foot sole for ground detection. No absolute sensors have been installed to fix the origin of the encoder.
Control algorithmsTask of robot are distributed in a software architecture by layers. These layers can be divided: + hardware interface: this layer contain the software drives. + axis control: this layer performs the control of individual robot joint. + leg layer control: this layer is in charge of coordinating all three joints in a leg to perform coordinated motion . +leg kinematics: this layer contain the direct and inverse kinematics function of a leg. +trajectory control: this mode is in charge of coordinating the simultaneous motion of four legs. +stability mode: determines whether a given foot position configuration is stable. +Gait generator: general the sequence of leg lifting and foot placement to move the robot in a stable manner. +graphic and user interfaces: contain the functions for ploting on the computer screen .
Indeed, there are currently three SILO4 robots in use testbeds as the Industrial Automation Institute . Otherwise The SILO4 has proven very reliable and suitable for its main purpose, and it has already been used as a testbed for many tasks. The SILO4 was demonstrate at the Second and Third International Conferences on Climbing and Walking Robot and has been offered as a common platform for the above mentioned purposes. To overcome the marketing and maintainability shortcomings plaguing the SILO4 commercial predecessors and to facilitate the use of this legged machine as a real common platform demonstrate. Therefore, we can see clearly that: this robot is really became a common testbed for experiments and discussion in areas such as artificial intelligence, perception, motion generation, terrain adaptation, and stability analysis. This is the new developmental step at the walking robot area.
Reference  K. Berns, The Walking Machine Catalogue. Available: http://www.fzi.de/ipt/WMC/walking_machines_katalog/walking_ machines_katalog.html  S.M. Song and K.J. Waldron, Machines That Walk: The Adaptive Suspension Vehicle. Cambridge, MA: MIT Press, 1989. IEEE Robotics & Automation Magazine 31  J.E. Bares and W.L. Whittaker, Configuration of autonomous walkers for extreme terrain, Int. J. Robot. Res., vol. 12, no. 6, pp. 535559, 1993.  J.E Bares and D.S. Wettergreen, Dante II: Technical description, results and lesson learned, Int. J. Robot. Res., vol. 18, no. 7, pp. 621649, 1999.  P. Gonzalez de Santos, M.A. Armada, and M.A. Jimenez, Ship building with ROWER, IEEE Robot. Automat. Mag., vol. 7, pp. 3543, Apr. 2000.  C.M. Angle and R.A. Brooks, Small planetary rovers, in Proc. IEEE/RSJ Int. Workshop Intelligent Robots and Systems, Ikabara, Japan, 1990, pp. 383388.  M. Fujita, AIBO: Toward the era of digital creatures, Int. J. Robot. Res., vol. 20, no. 10, pp. 781794, 2001.  H. Kitano, M. Fujita, S. Zrehen, and K. Kageyama, Sony legged robot.
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