Mitsubishi Heavy Industries Technical Review Vol. 53 No. 3 (September 2016)37

Car Crash Simulators Continue to Make Progress

M i ts u b i s h i H e a v y I n d u s t r i e s
Mechatronics S ystems Ltd.

A car crash simulator is a test device that can accurately reproduce the acceleration generated
in a vehicle cabin at the time of a car crash. They are used in the research and development ofpassive safety devices such as seats and seatbelts, air bags and headrests, doors, car interiors, etc.
This article describes the achievements made so far and future efforts for the car crashsimulator that Mitsubishi Heavy Industries Mechatronics Systems, Ltd. manufactures and sells.

|1. Features and major specifications
Our simulator is a test device that adopts an electro-hydraulic servo system. The test is
performed based on the principle that as shown in Figure 1, a carriage on which a test body ismounted is struck in the direction opposite to the collision direction by the piston of the servo
actuator to generate collision acceleration, which is the mainstream test method at present. The
servo actuator uses the accumulated oil of an accumulator as a power source and is controlled witha servo valve to make the acceleration on the carriage agree with the target acceleration. The main
specifications of this system are shown in Table 1.

Figure 1

System overview
Table 1 Example of main specifications
ItemSpecification value

RemarkMass of test body

2,000 kg at maximum

Firing acceleration

80 G at maximum

With a test body of 1,500 kg

Firing velocity

90 km/h at maximum＝25 m/s

Control displacement

1,700 mm at maximum＝Piston stroke

Control time

0.3 s at maximumResponse frequency

150 Hz at maximum

Mitsubishi Heavy Industries Technical Review Vol. 53 No. 3 (September 2016)38

The greatest feature of our servo actuator is that it adopts the meter-out method with servo
valves located on the hydraulic oil discharging side. This enables a high pressure start in thecylinder, and the natural frequency of the hydraulic excitation system is increased, allowing thehigh-fidelity reproduction of the waveform of collision acceleration to precisely match thehigh-frequency component.
Nine servo valves are operated in parallel, and the number of servo valves to be operated ischanged according to the magnitude of test acceleration, whereby a crash test can be made with awide range of acceleration, ranging from a frontal collision with a high acceleration to a rear-end
collision with a low acceleration．
In addition, a double-rods piston is adopted to prevent the movement of the piston before
firing, increasing the accuracy of the timing for piston movement to start. This is an important
requirement in operation timing adjustment tests of air bags or seatbelts.

|2. Efforts for improvement of basic performanceSince MHI put its first simulator on the market in 1997, we have made efforts to improve thebasic performance. The major targets of basic performance required for the reproduction of car
crash phenomenon with a higher fidelity are greater power (acceleration, velocity), larger
displacement, and higher response. The process of progress in these items is shown in Table 2.
Table 2 Process of progress of basic performance
Basic
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
performance
Mass of700kg
1,300kg
1,500kg
2,000kg
test bodyFiring40G
acceleration

75G

Firingvelocity65km/h

83km/h

90km/h1,000mmControl
displacement

1,300mm1,700mm～2015 2016-90G(Underdevelopment)

80G

2,200mm(Beingmanufactured)
0.6s(Beingmanufactured)
160Hz(Beingmanufactured)1,500mmControl
time

0.12s

0.15s

0.3s

Response
frequency

80Hz

100Hz

150Hz

First model

Ourdeliveries(Beingmanufactured)Meter-out method adopted|3. Efforts for development of test options
As vehicle technologies and technical knowledge have improved, new collision safety tests
have been introduced. Table 3 shows the safety standards and the history of the introduction ofnew car assessment testing in Japan.
Table 3Collision safety standards and the history of the introduction of
new car assessment testing (example in Japan)

Test item

1994 1995 ～ 1998 1999 2000 2001 ～ 2006 2007 2008 2009 ～ 2014 2015 2016

Full-wrap frontal
collision
Offset frontal
collision
Collision
safetySide collision
Rear-end collisionneck injury
protection
Child car seat

ActivesafetyCollision damage
reducing brake(Collision safety standards introduced(Against vehicle),New car assessment introduced)

Mitsubishi Heavy Industries Technical Review Vol. 53 No. 3 (September 2016)
39To correspond with such trends in testing, we have worked on developing various testoptions. The representative test options are shown in Table 4, and the development history anddelivery results for the test options are shown in Table 5. We have developed the test options
anticipating global testing trends and put them on the market. Among these test options, thepitching is notable, which allows vehicle motions in three degrees of freedom, that is, movementsin the back-and-forth and up-and-down directions and vertical rotation, with the addition of four
vertical servo actuators. Thus, a frontal collision test can be reproduced with a higher fidelity.
Table 4
Test option
PitchingToe board intrusion
Side collision

Rear-end collision

Table 5
Test option

Representative test options

Description
Purpose: To improve the accuracy of frontal collision tests
Content: Reproducing vehicle movements in the up-and-down
direction and vertical rotation at the time of a frontal collision
Purpose: To improve the accuracy of frontal collision tests
Content: Reproducing the phenomenon of toe board intrusion intothe cabin
Purpose: To reproduce a side collision test
Content: Making doors collide with passenger dummies while
door’s accelerating and decelerating
Purpose: To improve the accuracy of rear-end crash neck injury
protection performance tests
Content: Improving the accuracy of low-acceleration waveforms
by variable control of the number of servo valves

Remarks
Addition of four verticalactuators and special
carriage
Two degrees of freedom
motions of parallel
movement and inclining
Addition of carriage and jigs
for side collision test
Standard equipment

Development history and deliveries for the representative test options
1997 ～ 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 ～2016～(Beingmanufactured)

PitchingToe board intrusion
Side collision
Rear-end collision

Hereafter, equipped as standard.

|4. New efforts
The global trends in automobile collision safety technologies that we pay attention to aresolutions to small overlap crash tests, the spread of the use of collision damage reducing brakes,
and self-driving car. In connection with these trends, we consider that the development targets
shown in Table 6 will be required for our simulator in the future.
We will continue to make aggressive efforts toward the realization of the new development
targets in the future.
Table 6
Trend in collision safety technology

Future development targets

Development target

Description

Small overlap test

Yawing device

Reproducing the horizontal rotational movement of thevehicle in a small overlap crash test

Collision damage reducing brake

Prebrake-capable actuator

An actuator that can simultaneously reproduce thebehaviors of a collision damage reducing brake andcollision acceleration

Self-driving compact car

Actuator for compact car

An actuator that can be operated for collision
waveforms typical in compact cars which are expectedto spread as self-driving cars, electric cars, etc.