Sensors for Humanoid Robot

1. Sensors for Humanoid Robot Daniel Baptista1 Filipe M. T. Silva1 Vítor M. F. Santos2 1 Department of Electronics and Telecommunications 2 Department of Mechanical Engineering University of Aveiro, PORTUGAL

2. Overview • Introduction • Sensors for humanoid • Feet Sensors • Strain gauges • New Solutions • Load cell • The linear variable differential transformer (LVDT) • Capacitive sensors • The pressure linear potentiometer • Multi-Axis Force/Torque Sensor • Accelerometers • Gyroscope • Electronic Magnetic Compasses • CCD Camera

3. Introduction • Complete humanoid model • 22 degrees of freedom • Weight - 5 kg • Height - 60 cm • Max. width - 25 cm • Foot print - 20  8 (cm2) • Actuation • Servomotors with transmission belts • Sensors • A CCD Camera • Servos’ position (through its internal potentiometers) • Sensitive feet to applied forces • Accelerometers/Inclinometers • Gyroscopes

4. Envisaged sensorial capabilities Vision unit (on the head) Gyroscopes for angular velocity GYROSTAR ENJ03JA from MURATA Accelerometers for accelerations and inclinations Potentiometer for position feedback (HITEC Motor) ADXL202E from ANALOG DEVICE Motor electric current Sensitive feet Strain gauges on a slightly compliant material

5. Feet sensors • The strain gauges sensors esteem the Humanoid’s body balance • There are 4 strain gauges sensors on each foot. They are used to… • measure ground reaction forces • calculate the location of the Center of Pressure (CoP)

6. Feet sensors • The first version of strain gauges amplifier • No temperature compensation • Unbalanced Wheatstone bridge

7. Feet sensors • The second version of strain gauges Amplifier • High consumption of current • Bad contact in connectors the white board

8. Feet sensors • The third version of strain gauges amplifier • The mechanical screw adjust in the feet introduces perturbations • The potentiometer in the bridge causes problems • PCB Design • But, we are not satisfied!

9. Feet sensors – New solution 1 • Load Cell • The load cell used piezoresistors sensors in Wheatstone bridge • The force sensor operates on the principle that the resistance of • silicon implanted in the piezoresistors will increase when the resistors flex under an applied force.

10. Feet sensors – New solution 2 • The linear variable differential transformer (LVDT) • The transformer has three solenoidal coils placed end-to-end around a tube. The centre coil is the primary, and the two outer coils are secondaries. • A cylindrical ferromagnetic core, attached to the object whose position is to be measured, slides along the axis of the tube. • As the core moves, these mutual inductances change, causing the voltages induced in the secondaries to change. • The coils are connected in reverse series, so that the output voltage is the difference between the two secondary voltages.

11. Feet sensors – New solution 3 • Capacitive sensors • Capacitive sensors measure the distance between two plates via their capacitive effect

12. Feet sensors – New solution 4 • The pressure linear potentiometer • Implementation in Sony’s SDR-4X and suspected in QRIO • There are 4 force sensors in the foot sole. The sensors are specially designed diaphragm type sensor. The measurable range is 0~5 kg and the resolution is 10g.

13. Feet sensors – New solution 5 • The Multi-Axis Force/Torque Sensor system measures all six components of force and torque • Strain gauge sensor is attached to each measurement beam and each beam measures only one component of translational force.

14. Feet sensors – New solution 5 • Honda’s ASIMO utilizes six-axis force sensors in each foot of the robot. • These sensors measure forces and moments in all three directions as seen at the ankle.

15. Accelerometer/Inclinometer • The Accelerometer/Inclinometer used are ADXL202E (Analog Devices). • The ADXL202E will measure accelerations with a full-scale range of ±2 g. • The ADXL202E can measure both dynamic acceleration (e.g., vibration) and static acceleration (e.g., gravity). • When the accelerometer is oriented so both its X and Y axes are parallel to the earth’s surface it can be used as a two axis tilt sensor with a roll and a pitch axis.

16. Accelerometer/Inclinometer • Circuit of conditioning signal for Accelerometer /Inclinometer

17. Accelerometer/Inclinometer • Gravity acceleration measurement • Dynamic acceleration (gravity + dynamic moving) • Static acceleration (gravity)

18. Gyroscope • Piezoelectric Vibrating Gyroscopes • The gyroscopes is an angular velocity sensor that uses the phenomenon of Coriolis force, which is generated when a rotational angular velocity is applied to the vibrator.

19. Gyroscope • Piezoelectric Vibrating Gyroscopes (GYROSTARr) (muRata)

20. Electronic Magnetic Compasses • Electronic Compasses • Two-axis magnetic compasses measure the horizontal vector components of the earth's magnetic field using two sensor elements in the horizontal plane but orthogonal to each other.

21. CCD Camera • Unibrain Fire-i Digital Board Camera

22. CCD Camera • OpenCv the image processing • Color Filter • Template match

23. Sensors for Humanoid Robot EndThank you Daniel Baptista1 Filipe M. T. Silva1 Vítor M. F. Santos2

24. Power Management • Low Dropout Linear Regulator UCC283-5 3A (Texas Instrument) • PCB Design