Engineering Solutions to Build an Inexpensive Humanoid Robot Based on a Distributed Control Architecture Vítor M.F. Santos 1 and Filipe M.T. Silva 2 1 Department of Mechanical Engineering, University of Aveiro, PORTUGAL  2 Department of Electronics and Telecommunications, University of Aveiro, PORTUGAL  UNIVERSITY OF AVEIRO Centre for Mechanical Technology and Automation Institute of Electronic Engineering and Telematics Sensorial CapabilitiesSensitive Force Introduction Actuators Mechanical Design Power Requirements 6 DOFs per leg  Spherical joint on the hip  Simple joint on the knee  Universal joint at the foot 6 DOFs per leg  Spherical joint on the hip  Simple joint on the knee  Universal joint at the foot  Motors  Max current: 1.2–1.5 A per motor (big size model)  Electronics and control  Estimated to less than 200 mA per board  a total of ca. 1.5 A  Voltage Levels  5 V for logic; 6.5 V for motors  Two ion-lithium batteries installed  from Maxx Prod  7.2 V/9600 mAh per pack  Max sustained current of 19A  Each weights circa 176g  Confined to 373765 (mm 3 ) Accelerometers for accelerations/inclinations GYROSTAR ENJ03JA from MURATA ADXL202E from ANALOG DEVICE Vision unit (on the head) Motor electric current Serial power resistor Sensitive feet Strain gauges on a slightly compliant material Potentiometer for position feedback (HITEC Motor) Potentiometer for position feedback (HITEC Motor) ApplicationModelMass (g)Torque (Nm) Arms & small torque jointsHS85BB~ Legs & high torque jointsHS805BB Foot Ankle Lower leg Upper leg Lower hip Upper hip Hip Pelvis Trunk Neck Head base Shoulder Arm Forearm 3 DOFs per arm Neck & head accounts for 2 DOFs Trunk with 2 DOFs FINAL PLATFORM 3D model with 600+ components and 22 DOFs FINAL PLATFORM 3D model with 600+ components and 22 DOFs  Objectives/Motivation  Develop a humanoid platform for research on control, navigation and perception  Offer opportunities for under & pos-graduate students to apply engineering methods and techniques  Build a low-cost humanoid robot using off-the-shelf technologies, but still aiming at a fully autonomous platform  Why not a commercial platform?  Versatile platforms imply prohibitive costs!  Reduces involvement at lowest levels of machine design  Design Concerns  Distributed control architecture due to the complexity  Modularity to ease development & scalability  Rich sensorial capabilities  A device was custom-made using strain gauges properly calibrated and electrically conditioned  Four strain gauges arranged near the corners of the foot Gyroscopes for angular velocity  Static-dynamic simulations were carried out to estimate motor torques  Best low cost actuators in the market are Futaba RF servos or similar (HITEC,…)  Available models best suited for our application are:  Additional mechanical issues for motors  Use gear ratios up to 1:2.5 to rise torques  Use tooth belt systems for easier tuning  Use ball bearings and copper sleeves

Engineering Solutions to Build an Inexpensive Humanoid Robot Based on a Distributed Control Architecture Vítor M.F. Santos 1 and Filipe M.T. Silva 2 1 Department of Mechanical Engineering, University of Aveiro, PORTUGAL 2 Department of Electronics and Telecommunications, University of Aveiro, PORTUGAL Ongoing/Open IssuesConclusions Control Architecture Local Control Boards Control Level Units Low Cost… How Low?  Distributed control system  A network of controllers connected by a CAN bus  A master/multi-slave arrangement  Each slave controller is made of a PIC device with I/O interfacing  Asynchronous communications  Between master and slaves: CAN bus at 1 Mbit/s  Between master and high level controller (currently serial RS232 at baud)  Master and slave boards have a common base upon which a piggy-back unit can add I/O  sensors, communications …  Main control unit  Global motion directives & high level planning  Vision processing  Interface with possible remote hosts  1 Master CAN controller  Receives orders to dispatch to the slaves  Queries continuously the slaves and keeps the sensorial status of the robot  currently does it at ca. 10 kHz  7 Slave CAN controllers  Generate PWM for up to 3 motors  Interface local sensors  Can have local control algorithms  Servomotors  Big size: ~50 € x 14 -> 700 €  Smaller size: ~30 € x 8 -> 240 €  Miscellaneous electronic components  Total -> ~300 €  Aluminium gears and belts  Total -> ~300 €  Batteries  ~80 € x 4 -> ~320€  Sensors (except camera)  Negligible (<100€)  Raw materials (steel, aluminium)  Negligible (<100€)  Total ~ €2000  Excluding manufacturing and development costs (software, etc.)  Still missing:  Vision unit, central control unit (PC104+), lots of software  First humanoid motions  The robot is able to stand, lean on sides/forward/backward  Primitives locomotion motions have been achieved  Next concerns for the platform  Joint position feedback from dedicated sensor (not servo’s own!)  Safety issues to automatic cut of power on controller failure  Better adjustable tensors for belts  Selection and installation of central control unit (Embedded Linux)  Selection and installation of the vision unit (FireWire..?)  Research concerns  Localized/distributed control algorithms  Elementary gait definition  …  A highly versatile platform is possible to be built with constrained costs and off-the-shelf components  The distributed architecture shows several benefits:  Easier development  Easier debugging  Modular approaches  local controllers using piggy-back modules  Localized control  based on local perception and global directives  The selected technological solutions ensure a platform for research, mainly on:  Control algorithms  Perception  Autonomous navigation  Accelero- meters  Serial COM for master  Strain gauges conditioning  PIGGY-BACK BOARDS Main Control RS232 Master CANBUS Slaves UNIVERSITY OF AVEIRO Centre for Mechanical Technology and Automation Institute of Electronic Engineering and Telematics