Mitsubishi Heavy Industries Technical Review Vol. 61 No. 2 (June 2024)
1

Development of Ride Experience System toEvaluate Comfort of Automated Guideway Transit
Using Virtual Reality Technology
AKIHISA KAWAUCHI*1

TOSHIYUKI WADA*2

YUKIHIDE YANOBU*3

KOJI UCHIDA*1TOSHIFUMI KUDO*4

In recent years, the need to improve the comfort of various types of vehicles has greatlyincreased. Mitsubishi Heavy Industries, Ltd. has continued to improve the ride quality of its AGT(automated guideway transit) products by reducing the vibration of the vehicle through variousmeasures. Until now, implementation of actual vehicle running tests were needed to verify the ride
experience effected by such measures. At this time, we have developed a portable experiencesystem using VR (virtual reality) and a motion chair where one can experience the actual ride of avehicle. With this system, various verifications are possible without running actual vehicles byreproducing the feeling of a ride similar to that of the actual running vehicle. In this report, wewould like to describe our efforts.

|1. Introduction
AGT is a new transportation system that operates on rubber tires. Compared to standard
railways, AGTs can make tighter turns and handle steeper grades, providing greater flexibility inroute planning. AGTs have been widely introduced in Japan and overseas as a means to carrypassengers between airport terminals and as intra-city transportation systems(1).
Conventionally, vibration acceleration occurring in an AGT vehicle while running on thetarget route has been predicted using detailed numerical simulations based on MBD (multi-bodydynamics) technology, and measures to reduce such vibration have been considered in order toimprove ride comfort. However, even when the degree of vibration acceleration is predicted in anumerical simulation, it is difficult for designers and customers to imagine how comfortable theride would be. Consequently, fabricating an actual vehicle and running it has been required in orderto check ride quality.
One method often employed by major railroad companies and automobile companies toexperience the ride of an actual running vehicle is to use a large simulator with full-scaleequipment, but this requires significant time and expense. In addition, when customers fromoverseas or other distant places are involved, it is necessary for them to come to the factory wherethe equipment is located to experience the ride. To address these issues, we have combined VR anda motion chair to construct a portable and simple system that enables a person to experience theride comfort of the vehicle. This report describes our efforts to construct this system.

|2. Overview of ride experience system
2.1

System configuration

The overall configuration of the ride experience system is shown in Figure 1. The motion
chair is a Stewart platform-type device using six electric actuators to support the seat and has highportability, and operates on a household power supply (100 VAC). The seat of the motion chair is aG-Fit(2), which is used in AGTs designed and manufactured by us, such as the 7300 and 7500 seriesof Yurikamome (a new transportation system operating through Tokyo Waterfront City), and isinstalled using fittings. The PC used for control sends a signal to operate the motion chair, and also
*1

Chief Staff Researcher, Intelligent Machine Systems Research Department, Research & Innovation Center*2

Advanced Design Center, Technology Strategy Office*3Intelligent Machine Systems Research Department, Research & Innovation Center*4

Chief Staff Researcher, Vibration Research Department, Research & Innovation CenterMitsubishi Heavy Industries Technical Review Vol. 61 No. 2 (June 2024)
2outputs the video image and sound for the HMD (head-mounted display) that displays the VR
video image. As input data for displacement of the motion chair, simulation results from the MBD
analysis were used, but actual running data can also be used. Although the system is basically acombination of commercially available products, a highly immersive experience is created byaccurately synchronizing the video image, vibration, and sound.

Figure 1

2.2

Configuration of ride experience system

Acquiring actual running data for verification

In order to verify the developed ride experience system, vibration data of the actual running
car is necessary. To acquire this data, as well as video images and sound for the VR, data of
high-speed AGT vehicles(1) running on our Mihara test line(3) were used. Vibration data necessary
to calculate the amount of displacement which is used to control the motion chair was acquired
using a strain accelerometer and a gyro sensor, which is an angular rate meter, and is installed
under the G-Fit seat. Measurements were taken with a person sitting in the seat. As shown in
Figure 2, to acquire data during actual running, a 360° camera was installed at eye level of aperson sitting in the seat and was used to record a video image of the inside of the vehicle. Anambisonics, binaural microphone capable of recording 360° surround sound was positioned near
the person’s ear. By reflecting the acquired data in the ride experience system, a ride with vibration,
video image, and sound similar to those in an actual running vehicle can be experienced.

Figure 2 Recording video images and soundsof actual running vehicle

Mitsubishi Heavy Industries Technical Review Vol. 61 No. 2 (June 2024)3

2.3

Reproduction of actual running vibration

Among the results of comparison of the vibration measurement on actual vehicle and theresults of reproduced vibration using the motion chair, an example of acceleration on verticaldirection for the vibration acceleration speed at each 1/3 octave band is shown in Figure 3. Incompliance with JIS B 7760-2:2004 (ISO 2631-1: 1997) which is used to consider the effect ofvibration on the human body on health, comfort, and vibration perception, the frequency-corrected
acceleration effective value, to which the frequency coefficient depending on the direction ofacceleration action, posture, etc. has been applied, can be reproduced within ±10% accuracy of theactual measurement. Furthermore, reproducibility deteriorates at 10Hz and higher because it is outof the control frequency range of the motion chair.

Figure 3

2.4

Vibration reproduction by a motion chair

Evaluation of immersiveness of system

This system combines the vibrations, video images, and sounds obtained from an actual
running vehicle as shown in Figure 4. In this system, a person sits in the same seat as that of anactual vehicle and experiences the same level of vibration as that of an actual running vehicle,
along with the video image and sound through HMD and surround headphones, creating a ride
experience that feels similar to that of an actual running vehicle.

Figure 4 Display screen of the system

A questionnaire-based evaluation was conducted with 20 participants of various ages in orderto determine which elements of this system strongly contribute to improved immersiveness. Resultsof the evaluation are shown in Figure 5. The participants compared the immersiveness of anexperience case with the previous-condition case they experienced and rated immersiveness on a5-point scale, where 1 represents feeling more immersiveness than that of the previous case and 5
represents feeling less immersiveness. When the degree of freedom to operate the motion chair waschanged from 6 (3 translation directions and 3 rotation directions) to 3 (only 3 translation
directions), no significant difference in the ratio of participants who felt immersiveness wasobserved. From this, reproduction using only the vibration component of 3 translation directions
could be confirmed to be sufficient since AGT runs without any significant inclination. However,Mitsubishi Heavy Industries Technical Review Vol. 61 No. 2 (June 2024)
4

when 6-degree freedom with sound is changed to only 3-degree freedom vibration, the ratio ofparticipants who felt an immersiveness decreased, and the ratio of those who felt the connection
between the images and movements was strange increased. This indicates that sound is important in
the improvement of immersiveness in the ride experience system.

Figure 5

Results of immersiveness evaluation|3. Utilization of this system
With this system, a simplified vehicle riding experience, without actually riding in a vehicle,
is possible. The following are examples of utilization of this system.
(1) Experiencing the results of a running simulation
An example of an MBD model that can calculate the vibration acceleration generated by avehicle through a simulation is shown in Figure 6. This model is a combination of modeled AGT
components and is supported by air springs and vertical dampers in the vertical direction, while
the body and bogie are coupled by parallel links in the front-back direction(4). The bogie has anaxle and tires driven by a motor via gears, and a guide steering mechanism is used to steer thetires. The model track on which the AGT vehicle runs reflects the track alignment of the actualroute and the unevenness of typical AGT track surfaces and guideways. The vehicle and trackmodels are combined to predict vibration acceleration by simulation, and the results are used tocommand the motion chair. In addition, a video image of the running vehicle created by 3D CG,etc. is displayed on HMD in combination with the running sound of a similar vehicle. As a result,
this system can create a ride experience before the actual route and vehicle are completed.

Figure 6AGT vehicle MBD modelMitsubishi Heavy Industries Technical Review Vol. 61 No. 2 (June 2024)
5(2)Experiencing the effect of improved ride comfort
Changes in car vibration acceleration predicted by measures to improve ride comfort
which have been considered in the running simulation can be reproduced and experienced prior
to manufacture or modification of the actual car. As such, vibration characteristics felt by actual
passengers which are necessary to improve ride comfort can be evaluated not only numerically
but also physically, and effective measures can be considered while reducing running test costs.
In the case of AGTs, the track surface may deteriorate over many years of operation, andrepairs may be necessary to improve the track surface. By evaluating how such repairs affectthe reduction of vibration acceleration in the vehicle not only numerically but also by
experiencing it through this simulator, the need for track repairs can be better understood.
(3) Remotely experiencing a ride using VR video images
When a person experiences a ride using this system, the image displayed on the HMD
changes depending on the movement of the person's head. By recording the video image
displayed on the HMD, the ride can be experienced in a simplified manner using the recorded
video and sound with only the HMD, without the motion chair. In this case, the recorded video
image reflects eye movement in response to the actual running vehicle vibration andimmersiveness can be improved to a greater extent than that just with a normal video image
projected on the HMD. Consequently, even customers in remote areas who would havedifficulty visiting a site equipped with a motion chair can experience the ride with highimmersiveness.

|4. Conclusion
In order to construct a system to experience the ride comfort of the vehicle, vehicle
acceleration from an actual running vehicle was measured, and a 360° video image with sound wasrecorded while running the vehicle. A commercially available motion chair was used to accurately
reproduce the measured vehicle acceleration, the video was displayed using HMD and the soundwas played back using headphones. As a result, a system that can create a ride experience similar tothat of an actual running vehicle could be constructed. With this system, the effect of improvements
in ride comfort can be verified by reproducing the simulation results of the running vehicle basedon MBD analysis, even before the actual vehicle is completed.
We plan to actively apply this system to actual construction projects in order to reduce thetime and cost required for an actual running test, and seeks to promote the system to our customers.
In addition, we wish to promote the application of this technology, which combines VR and amotion chair, not only to new transportation system vehicles, but also to our other vehicle products
such as ships and aircraft.

References
(1)
(2)

(3)
(4)

M. Hoshi et al., High-speed Automated Guideway Transit System, Mitsubishi Heavy Industries TechnicalReview, Vol.52 No.1 (2015)"7300 Series" Railway Carriages Win "Good Design Award 2014" -- Cars for Automated Guideway
Transit System "Yurikamome" Line Also Selected Among "Best 100" --, Mitsubishi Heavy Industries
Press Information 2014-10-01 No.1837
Enhancement and Utilization of Multipurpose Integrated Highly-Advanced Railway Applications(MIHARA) Test Center, Mitsubishi Heavy Industries Technical Review, Vol.53 No.3 (2016)
M. Masukawa et al., Development of New Type Bogie for Automated Guideway Transit, Journal of theSociety of Mechanical Engineers 2014.9 Vol.117 No.1150 (in Japanese)