Development of Magnetostrictive Load Sensor for Motorcycle

Development of Magnetostrictive Load Sensor for Motorcycle
2002.05.14
Technical
Papers and
Articles
Development of Magnetostrictive
Load Sensor for MotorcycleMeasurement Robot
Yutaka Mizuno Tsuyoshi Kubota
● Advanced Technology Research Div.
Abstract
In order to improve the accuracy and efficiency of evaluation of increasingly high-performance
motorcycles, we at Yamaha Motor have developed a control system for automated operation of
motorcycles by human-shaped robots. For the indispensable shift load sensor in the system, we had
originally used a strain gauge type load cell but were unable to get satisfying results with it regarding
sensor sensitivity when subjected to engine vibration conditions, strength and response. To solve
these problems, we tried using a magnetostrictive sensor for the first time. In tests in actual use we
found that the magnetostrictive load sensor satisfied the requirements of operating conditions for a
motorcycle operation control system and measurement system.
1
INTRODUCTION
Recently, motorcycles are having high functionality, high performance, and high speed. Then,
riders must be skilled especially during a driving evaluation test. Therefore, a control system using
anthropomorphic robot for auto driving of motorcycle has been developed in order to improve the
development efficiency. In this control system, the anthropomorphic robot controls the accelerator,
shift, and clutch operations to make the driving bench test with auto operation possible. This paper
describes the magnetostrictive load sensor, which is absolutely required for this control system.
2 MEASUREMENT SYSTEM FOR MOTORCYCLE DRIVING PERFORMANCE
2.1 EVALUATION TEST EQUIPMENT
Figure 1 shows the photo of the motorcycle measurement system using the robot. In this
measurement system, the anthropomorphic robot controls the accelerator, shift, and clutch operations
to make the driving bench test with auto operation
possible. Use of the robot makes it possible to
improve the accuracy and repeatability of the test
data.
Figure 1 Motorcycle test using anthropomorphic robot
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Development of Magnetostrictive Load Sensor for Motorcycle-Measurement Robot
Figure 2 shows a wind tunnel apparatus for
motorcycle driving test. Winds flow from front
side of a motorcycle at the same speed as running
speed. And motorcycle stays on the Chassis
dynamo.
2.2 AUTO DRIVING CONTROL SYSTEM
Figure 3 shows the auto d r iving cont rol
system. The driving patterns can be controlled
automatically using the built-in driving programs.
Figure 2 Wind tunnel apparatus
And the operator pressing only the start button in the operation room carries out the evaluation test.
The control data is sent into the bench through the I/O control units in order to give drive
commands to the robot, and to set the environment and load conditions. At the same time, the
statuses of various sensors inside the bench are also sent to the controller through the I/O control
units. The controller is built in the control panel and designed to monitor the driving status and
record the measured values transmitted from the sensors into the logger.
Figure 3 Block diagram of entire measurement system
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Development of Magnetostrictive Load Sensor for Motorcycle-Measurement Robot
SHIFT LOAD SENSOR FOR MEASUREMENT ASSIST ROBOT
3.1 MEASUREMENT ASSIST ROBOT
Figure 4 shows the control block diagram of
the measurement assist robot. Relevant actuators
and sensors are mounted in the accelerator, clutch,
and shift operation systems. The robot plays
two important roles. First, the shift change and
accelerator adjustment controlled automatically
Figure 4
Control block diagram of measurement
assist robot
by actuators to set the output of the motorcycle.
Second, the air flow adjustment around the engine, as if a rider is actually sitting on the motorcycle.
In the driving evaluation, the air flow around the engine including the driver’s body may turn
into problems. The upper part of the driver’s body does not affect the air flow around the engine.
Therefore, the robot simulates only the lower part of the driver’s body.
3.2 JUDGEMENT OF SHIFT CHANGE
It is very important for auto driving that it is
judged properly whether or not the shift has been
changed correctly. Normally, it cannot be judged
properly by detecting only the shift stroke. So,
the measurement system detects the shift stroke
and shift load at the same time. Figure 5 shows
changes in shift load when the shift pedal is
operated. Generally, when the shift is changed
1) Shift success
successfully, it is found that the load decreases
halfway during increasing of the shift load.
(Figure 5-1) If the shift is changed incorrectly, the
load does not decrease until the shift operation is
released. (Figure 5-2)
Then, by detecting both the shift load and
shift stroke at the same time, it is possible to
judge whether or not the incorrect shift change
occurred. Therefore, a highly accurate sensor was
strongly required, which can detect changes in
2) Shift mistake
shift load under engine vibration conditions.
Figure 5 Changes in shift load
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Development of Magnetostrictive Load Sensor for Motorcycle-Measurement Robot
INITIAL TYPE OF SHIFT LOAD SENSOR (STRAIN GAUGE TYPE)
The shift load sensor unit is used not only
to detect the shift load, but also to connect the
linear actuator with shift pedal. Figure 6 shows
the layout of shift load sensor. And, it was
fi rst attempted to detect the shift load using a
commercially available strain gauge type load
Figure 6 Layout of shift load sensor
cell. However, since the detection sensitivity of
this sensor was low, accuracy necessary for the control could not be obtained. So, the sensor often
could not detect incorrect shift change.(Figure 7-1)
Additionally, when the sensor having higher sensitivity was used, the sensor was broken within
a short time due to insufficient strength. (Figure 7-2) If this type of sensor was broken during
auto driving, the actuator was separated from the shift pedal, causing the engine control to become
impossible.
1) A detected signal
2) The damaged sensor
Figure 7 Initial type of shift load sensor (strain gauge type)
5
NEW TYPE OF SHIFT LOAD SENSOR (MAGNETOSTRICTION TYPE)
5.1 MAGNETOSTRICTIVE LOAD SENSOR
A magnetostrictive load sensor has been newly
developed to solve the problems of the strain
gauge type sensor. Figure 8 shows the outside
view of the newly developed magnetostrictive load
sensor.
Figure 8
Outside view of magnetostrictive load
sensor
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Development of Magnetostrictive Load Sensor for Motorcycle-Measurement Robot
This type of a sensor uses a change of the inductance accompanying strain. Because the rate
of change is higher than that of the strain gauge type load cell, it has high sensitivity. And it can
constitute a sensor with intensity higher than the strain gauge type load cell.
This sensor is small and lightweight, and has excellent responsibility and load resistance.
Additionally, the displacement during measurement is very small. Furthermore, a low
manufacturing cost can also be achieved since the structure is simple.
Figure 9 shows an example of load characteristics of the sensor. Table 1 shows the characteristics
of the sensor at this time.
Figure 10 shows the durability of this sensor. If
this sensor is operated within the allowable load
range, it can be operated at least 106 times. Blue
line and brown line mean stable sensitivity.
Table 1 Characteristics of magnetostrictive load sensor
The maximum permissible load
800N
Non-Iinearity
3%
Hystersis
5%
Temperature characteristic
Figure 9 Example of load characteristics
Figure 10
0.25mV/C
Repeated load test results
5.2 MAGNETOSTRICTIVE SHIFT LOAD SENSOR UNIT
We have developed a new shift load sensor
unit using the newly developed magnetostrictive
load sensor. Figure 11 shows the status how this
sensor unit is mounted on the actual motorcycle.
This sensor has high sensitivity and excellent load
resistance compared to the initial type of shift
load sensor.
Figure 11 New-type shift load sensor mounting status
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Development of Magnetostrictive Load Sensor for Motorcycle-Measurement Robot
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F i g u r e 1 2 s h ows t h e s t r u c t u r e o f t h e
magnetostrictive shift load sensor unit. This
sensor u n it ha s a st r uct u re, i n wh ich t he
magnetostrictive load cell is sandwiched by the
springs. Thus, this structure protects the sensor
from the impact and/or overload. Additionally,
even if a trouble occurred in the sensor, the
sensor holder is not damaged. So, the remoteshift operation can be performed through the
operation panel by changing the operation mode
to the manual mode.
Figure 12 The structure of the sensor unit
5.3 RESULTS OF APPLICATION OF LOAD SENSOR UNIT TO MEASUREMENT
SYSTEM
Figure 13 shows the obtained load signals. As the sensitivity is improved when compared to the
initial type shift load sensor, the incorrect shift change is detected properly. Thus, the measurement
of the test results can be made automated.
Figure 14 shows an example of the test course driving pattern. In addition to this driving pattern,
this measurement system has been used for auto driving with various driving patterns until now. It is
said that the system has been operated properly.
Figure 13
Results of measurements using
magnetostrictive shift load sensor
Figure 14 Test course driving pattern
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Development of Magnetostrictive Load Sensor for Motorcycle-Measurement Robot
CONCLUSION
In the auto driving evaluation system of the motorcycle using the measurement assist robot, a
magnetostrictive shift load sensor has been newly developed to detect the shift load. Using this load
sensor, the shift change can be controlled properly in the auto driving evaluation system.
This sensor was mounted on a motorcycle and used for the evaluation with various driving
patterns. As a result, it was verified that this sensor provides the sensitivity and strength necessary
for the control.
Development of the magnetostrictive shift load sensor makes it possible to detect incorrect
shift change, which was the subject in the conventional measurement system, in the auto driving
evaluation system of the motorcycle using the measurement assist robot. As it is planned to bring
this measurement system to the commercial stage, it will be promoted to make the sensor unit
more compact and lightweight. And, it is also planned to provide various measurement items by
improving the reliability and compatibility with the hardware. This magnetostrictive sensor is small,
lightweight, and less expensive, and provides the excellent sensitivity, strength, and responsibility,
which are sufficient for practical use. Therefore, this sensor is applicable to not only this
measurement system, but also a wide variety of other control systems. We will strive to pursuit this
possibility.
■ LITERATURE
1) Development of Magnetostriction-type Load Sensor for Measurement System Using Motorcycle
Testing Robot,
Yutaka Mizuno, Kubota Tsuyoshi, Yamaha Motor Co., Ltd. 2002.03 SAE World Congress
2) Study of motorcycle shift system
Katsumi Fujimoto, Naoki Inoue, Katsumi Yamazaki, Honda Motor Co., Ltd.
1990 Vol. 2 , Honda R&D Tech Review
3) Quantification of Motorcycle Shift Feeling
Hideo Suda, Suzuki Motor Corporation
1997 Vol. 51, Journal of Society of Automotive Engineers of Japan
YAMAHA MOTOR TECHNICAL REVIEW
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