eRide
OPUS 6/
eRide
OPUS 7 GV-8620/ GV-8720
Dead Reckoning User
’
s Guide
SE16-900-002-02
16
FURUNO ELECTRIC CO., LTD. All rights reserved.
9 Important Notice
9.1 Important Notice for IMU Sensor
Please design and implement based on the data sheet of IMU sensor. In addition, please verify the products to
achieve the target performance.
9.2 Characteristics of IMU Sensor
The DR receiver is designed to provide accurate performance by estimating errors of bias and gain described
in the data sheet of IMU sensor. The performance may be degraded by influence of some characteristics not
described in the data sheet of IMU sensor.
9.3 Layout Design against Influence of IMU Sensor by External Environment Factor
Since the IMU sensor is a very sensitivity device against the following three external environment factors, keep
the layout design of IMU sensor based on the below guideline.
(1) Temperature factor
External temperature has a negative impact on the angular velocity and the acceleration of IMU sensor. In
order to avoid this influence, consider the following guideline of design.
a) Implement the IMU sensor apart from heat sources.
b) Protect influences of dynamic temperature change by surrounding air.
(2) Mechanical factor
The vibration and impulse against IMU sensor has a negative impact on the angular velocity and the
acceleration of IMU sensor. Below are examples to avoid this influence.
a) Implement the IMU sensor nearby the holding part of the board.
b) Clip the board by shock-absorbing material with labor.
c) Fix the unit or board, which IMU sensor is implemented, by screws.
(3) Other factor
Because of the gyro sensor and the accelerometer are MEMS devices, these devices have a resonant
frequency for operating MEMS mechanically and electric frequency characteristics internally. In case the
MEMS device has an external mechanical or electrical impact which is close to the frequency characteristics of
MEMS device, there is a risk of significant degradation regarding the output characteristics of sensor.
Therefore, user should design the circuit of surrounding area of sensor for preventing influences of external
mechanical vibration or electrical signal characteristics such as system clock signal.
9.4 Calibrating Operation
Good GNSS signal reception environment provides suitable calibration of IMU sensor. Therefore, install the
antenna on the place which good GNSS signals can be received. Also, take care that there is enough antenna
gain and no degrade of reception signal by noise on actual operation.
For calibrating the vehicle speed pulse, it needs to drive faster than 20km/h under good GNSS signal reception
environment. When an actual operation is traveling at a low-speed (ex. the bus drives in an urban area.), it
needs much time for calibration or the calibration may not be finished. Therefore, it is recommended to start
the actual operation after the calibration.
