Transcript A Study of Flexible Shoe System for Biped Robot

High-speed Pressure Sensor
Grid for Humanoid Robot Foot
Y. Takahashi, K. Nishiwaki, S.Kagami, H. Mizoguchi, H. Inoue
Digital Human Research Center
National Institute of Advanced Industrial Science and
Technology
2-41-6, Aomi, Koto-ku, 135–0064, Japan
[email protected]
PPT製作100%
Student ID ： M9920103
Student
： Kun-Hong Lee
Adviser
： Ming-Yuan Shieh
1
Outline








ABSTRACT
INTRODUCTION
SCANNING CIRCUIT
THIN FORCE SENSING RUBBER
SCAN METHOD IN THIS SYSTEM
EXPERIMENT
CONCLUSION
References
2
ABSTRACT



This paper describes a 32 × 32 matrix scan type high-speed
pressure sensor for the feet of humanoid robots that has 1[kHz]
sampling rate. This sensor has matrix scan circuit.
We adopted very thin(0.6[mm]) force sensing conductive rubber
sheet for high speed sensing. Each sensing area is 4.2 × 7.0[mm]
and can measure vertical force of approximately 0.25– 20[N].
Walking cycle of humanoid robot as well as human being is about
0.4–0.8[s] and dual leg phase is about 0.1–0.15[s]. The target of
the sensor is biped walk stabilization so that highspeed input is
important.
3
INTRODUCTION(1/3)
Fig. 1. Humanoid
robot H7
4
INTRODUCTION(2/3)



However, on uneven surface tactile information is becoming
important to control landing shock absorption and balance
control. We are working on a footstep planning technique on
uneven surface[1], but it is also vital to achieve by real sensor
and control system.
We developed a high-speed distributed force sensor with very
thin (0.6mm) force sensing conductive rubber.
The sensor system is equipped with AD converters both on the
column lines and row lines of the sensor electrode part.
5
INTRODUCTION(3/3)


The system runs about 1[kHz] with 14bits resolution at 4.2 ×
7.0[mm] grid for 32 × 32 points. Whole sensor area is same as
sole of H7 humanoid 135 × 228[mm].
This sensor element is classical key matrix scan sensor, but has
1[kHz] sampling rate which is the same as the lowest software
control cycle of our H7 humanoid robot system.
6
SCANNING CIRCUIT(1/3)



We use analog switch for current supply one by one, and read
output voltage with additional voltage following op-amp.
Therefore, there are 32 analog switch and ADC
Control flow is as follows: One analog switch becomes “High” and
after fixed weight time (default is 3.1[us]) column and row lines
voltage simultaneously read the voltages of each line.
It repeats until 32 analog switch lines becomes “High” once.
Then row lines data matrix(32×32, 2[kB]) and column lines data
matrix(32 × 32, 2[kB]), two matrixes data is transmitted to the
control PC.
7
SCANNING CIRCUIT(2/3)

Developed system is shown in Fig. 3 and Fig. 5.
Fig. 5. Sensor control cuicuit.
USB2.0 link send force image by
1[kHz]
Fig. 3. Electrode part of the sensor.
8
SCANNING CIRCUIT(3/3)

Electrodes which are shown in Fig. 4 are arranged in the shape of
a grid.
Fig. 4. Sensor grid size.
Each sensing area is 4.2 × 7.0[mm].
9
THIN FORCE SENSING RUBBER(1/2)
TABLE 1
FORCE SENSING RUBBER
RESISTER
Fig. 6. Force - resistance curve
10
THIN FORCE SENSING RUBBER(2/2)
Fig. 7. Relationship from load and measured voltage
11
SCAN METHOD IN THIS SYSTEM(1/3)

The system in this paper is equipped AD converters both on the
column lines and row lines of the sensor matrix(Fig. 8).
12
Fig. 8. Pressure sensor circuit diagram. (Example 3x3 matrix)
SCAN METHOD IN THIS SYSTEM(2/3)

As shown in a Fig. 8, when the colum line 1 is applied the voltage,
the following formula is led from Kirchhoff’s current rule at the
top row:
13
SCAN METHOD IN THIS SYSTEM(3/3)

Value of resistance
is found by taking the reciprocal of each
element of vector .
14
EXPERIMENT(1/5)

A. Experiment of static pressure

Static pressure was applied to the sensor.


A cylinder (Diameter: 20[mm] Weight: 1[kg]) was put on the
electrode unit. The scanning rate was set to 300[Hz]. The
experimental result is shown in Fig. 9.
The pressure was applied to the electrode part with conductive
rubber on the floor by human foot.
Fig. 9. Sylinder applies static
pressure to the
15
sensor
EXPERIMENT(2/5)



The pressure was applied to the electrode part with conductive
rubber on the floor by human foot.
A subject(male, weight:65kg, foot size:27cm) stood on the sensor.
By usual matrix scan method, the voltage of row lines is shown in
a Fig. 10. The right side of a Fig. 10 is a toe and left is the heel.
Fig. 10. ADC data foot
print (normal)
16
EXPERIMENT(3/5)


Although there is no pressure in fact, there are points which
seem to have impressed pressure(for example arch of a foot).
Fig. 11 shows a calculation result using the method in this paper.
The interference at each point is suppressed by this method.
Fig. 11. Foot print with
this method
17
EXPERIMENT(4/5)





Experiment of dynamic pressure
As the dynamic pressure, the subject(male, weight:65kg, foot
size:27cm) run on the sensor. Scanning rate was 300[Hz].
The result is shown in Fig. 12, it shows the relative time from first
frame.
There is almost no delay of the viscoelastic response of rubber,
because of very thin conductive rubber and simultaneous
measurement.
Interference at each point is suppressed also to dynamic
pressure by this method.
18
EXPERIMENT(5/5)
19
Fig. 12. Dinamic pressure is applied to the sensor unit using human
CONCLUSION






Matrix scan is achieved with a novel method.
Resistance at each sensing point is calculated by solving the
simultaneous equations from column and row lines voltage.
Interference by bypass current is suppressed by this method.
The high-speed(1[kHz]) sensor was realized by measuring voltage
simultaneously and thin(0.6[mm]) force sensing conductive
rubber.
Distributed pressure was successfully measured.
In the future, we will use this sensor for foot landing force
absorption and balance control of our humanoid robot.
20
REFERENCES









[1] Joel Chestnut, James J. Kuffner, Koichi Nishiwaki, and Satoshi Kagami.Planning biped navigation
strategies in complex environments. In IEEEInternational Conference on Humanoid Robots
(Humanoids2003), 10 2003.
[2] Satoshi Kagami, Masaaki Mochimaru, Yoshihiro Ehara, Natsuki Miyata,Koichi Nishiwaki, Hirochika
Inoue, and Takeo Kanade. Measurementand comparison of humanoid h7 walking with human being.
In IEEEInternational Conference on Humanoid Robots (Humanoids2003), 10 2003.
[3] Makoto Shimojo, Masatoshi Ishikawa and Kikuo Kanaya. A Flexible High Resolution Tactile Imager
with Video Signal Output. In IEEE International Conference Robotics and Automation , pp.384-391
1991.4.9-11
[4] W. E. Snyder and J. ST. Clair. Conductive Elastomers as Sensor for Industrial Parts Handling
Equipment. In IEEE Trans. Instrumentation and Measurement , IM-27-1 pp. 94-99 1978.
[5] J. A. Pubrick. A Force Transducer Enploying Conductive Silicone Rubber. In Proceeding 1st
Conference on Robot Vision and Sensory Controls , pp. 73-77 1981.
[6] S. Kagami, Y. Takahashi, K. Nishiwaki, M. Mochimaru and H.Mizoguchi. High-speed Matrix Pressure
Sensor for Humanoid Robot by using Thin Force Sensing Resistance Rubber Sheet. In Proceeding of
International Conference IEEE Sensors ,2004.
[7] Masatoshi Ishikawa and Makoto Shimojo. An Imaging Tactile Sensor with Video Output and Tactile
Image Processing. In The Society of Instrument and Control Engineers , Vol.24, no.7, pp. 662-669
1988 (in Japanese).
[8] W. D. Hills. A high-resolution image touch sensor. In International Journal Robotics Research , Vol.1,
no.2 pp. 33-44 1982.
[9] Genichiro Kinoshita, Tomonori Kimura, and Makoto Shimojo Dynamic Sensing Experiments of
Reaction Force Distributions on the Sole of a Walking Humanoid Robot. In Proceeding of the 2003
21 Systems ,10 2003.
IEEE/RSJ Intl.Conference on Intelligent Robots and