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AuthorsPo-Er Hsu (2013-01-28); recommended: Yeh-Liang Hsu (2013-02-10).
Note: This article is the Chapter 6 of Po-Er Hsu’s doctoral thesis “Development of an intelligent robotic wheelchair as the center of mobility, health care, and daily living of older adults.”

Chapter 6. Conclusion and future work

6.1  Conclusion

This thesis presents the development of the “intelligent Robotic Wheelchair” (iRW), which intends to redefine the wheelchair as the center of mobility, daily living, and healthcare of older adults. Technically, the iRW is composed of an omni-directional vehicle, a multiple-DOF seat adjustment mechanism, and an information/communication module to provide mobility aids and to support daily living and healthcare. Implementing robotic technologies on the wheelchair, the iRW enhances the usability of wheelchair to increase the independent living and social participation for older adults. Figure 6-1 shows the current prototype of the iRW, and Table 6-1 shows the specifications of the iRW.

Table 6-1. Specifications of the iRW

Characteristic

Specification

L×W×H

800×610×890 mm

Weight

28 kg

Mecanum wheel diameter

25.4 mm (10 inches)

C-LiFePO4 Battery

24 V, 9.6 Ah, 3.4 kg

Mobility assistance

speed

Forward

50 m/min (Max)

Backward

40 m/min (Max)

Sideways movement / Clockwise / Counterclockwise

25 m/min

Teleoperation / Indoor navigation

15 m/min

Seat adjustment

range

Initial height of the seat

414 mm

Seat elevation

370 ~ 488 mm

Tilt-in-space

22° (CW) / -15° (CCW)

Sideways movement

Varies with height of the seat, 140 mm at the initial height

Actuator (HIWIN LAS3-1)

Tensile / Thrust / Self-locking force

1200 / 1200 / 800 (Max, N)

Stroke

150 mm

Speed (maximum/ minimum load)

8 / 12 mm/s

Optical sensor accuracy

0.3175 mm/pulse

Voltage / Current

24 V / 2.5 (A, Max)

Chassis motor

(Motion Tech. EC Series)

Output

150 W

Speed

4,700 ± 150 rpm

Voltage / Current

24V / 3A (Max)

Brake

30 kgf/cm

Figure 6-1. The prototype of the iRW

The omni-directional vehicle of the iRW is equipped with four Mecanum wheels to facilitate movement with zero radius of rotation and in all directions, in particular, the sideways movement. From the results of the space utilization assessment, the iRW requires much less space than general electric wheelchairs in maneuvers such as “90° left/right turn”, “turns 180° in place”, and “maneuvers sideways”. Mobility assistance functions can be invoked by the wheelchair user, caregivers, or the iRW itself. Five operation modes—obstacle avoidance, joystick mode, handlebar mode, teleoperation, and indoor navigation—were developed for the mobility assistance functions of the iRW. From the functional test results, the handlebar mode has the highest operation efficiency, followed by the joystick mode. The teleoperation mode has the lowest operation efficiency. The priorities are assigned to the operation modes to avoid different modes disrupting each other and foster safety. Top priority is assigned to the emergency modes such as obstacle avoidance. Priorities are then assigned according to the operators of the modes (in descending sequence): wheelchair user, caregiver, and finally the iRW itself.

The user-configurable indoor navigation, which is the primary autonomous behavior, of the iRW, aims to reduce the operation load on the wheelchair user. The indoor navigation system uses the automated guided vehicle (AGV) as the design concept for route planning. In this indoor navigation system, the QR code contained directions of the reachable desired destinations is used to compose the virtual AGV track to achieve motion execution. The virtual AGV track can be reorganized by printing new QR code labels to deploy on the ceiling, so that the user have the flexibility and convenience of the path management and installation. The user interface and indoor navigation algorithm are implemented as an App in the tablet. Moreover, this system uses the camera and electronic compass, which are both built-in the tablet to reorganize QR codes on the ceiling and to obtain direction information. From the performance test results, the success rate of QR code recognition was increased when the distance between two QR codes was reduced from 11 m to 3.5 m. The performance test result is demonstrated that this indoor navigation system is practical for the home environment.

Seat adjustment design is of crucial importance to a wheelchair user. The multiple-DOF seat adjustment mechanism of the iRW is achieved by a four-axis Stewart platform. It is capable of adjustment in tilt-in-space, seat elevation, and sideways movement to support the needs of the wheelchair user at home, including comfortable sitting posture, pressure management, and transfer activities assist. The actuators are carefully arranged so that only one actuator needs to be controlled, enabling the wheelchair user to adjust the seat by simply pressing a button. A memory foam seat, which helps to relieve body pressure for better comfort, rests on the multiple-DOF seat adjustment mechanism. The armrests can be opened outward during transfer assist. This multiple-DOF seat adjustment mechanism is intended to increase the independence of the wheelchair user, while maintaining a concise structure, light weight, and intuitive control interface. From the orientation confirmed test, the 70 kg mass has slight effect on the stability. However, the user felt safe and stable while adjusting the seat of the iRW. Besides, it was demonstrated that the seat adjustment functions of the iRW can help the user to perform transfer activities more easily and more conveniently with less effort than the manual wheelchair.

6.2  Future work

The iRW provides innovative design concepts of the products to the wheelchair industry which is confronted with a decline in technology development, as described in Chapter 1. As shown in Figure 2, technologies developed in the iRW can be classified in to 11 modules under the three main categories, Stewart platform, omni-directional vehicle, and home telehealth. Figure 6-2 also serves as the patent portfolio of the iRW. Table 6-2 shows the patent list of the iRW.

Figure 6-2. Patent portfolio of the iRW

Table 6-2. Patent list of the iRW

Patent number

Title

Under review

Intelligent robotic wheelchair (TW, US)

US8,111,817

Portable tele-homecare monitoring system and method for the same

I312673

Portable tele-homecare monitor system and method for the same

I309785

Distributed data server and method for the same

I299260

Muti-vital sign detecting mat and algorithm and method thereof

I290699

RFID-based portable tele-homecare monitoring system and method for the same

I287976

Portable distance home vital signals monitoring system

I286714

Portable distance home vital signals monitoring system

Under review

A tele-homecare system with care delivery capability and method thereof

Under review

Distributed home telehealth and method thereof

Under review

Concealed motion detection apparatus and method thereof (TW, US, JP)

Under review

Stewart platform seat mechanism for the intelligent robotic wheelchair (TW, US)

Under review

Pressure ulcer prevention based on Stewart platform seat mechanism for the intelligent robotic wheelchair

I262873

Remote working vehicle

I318064

Remote monitoring and controlling for mobile system and method thereof

Under review

Telepresence robot and method thereof

Under review

Quick response code on automated guided vehicles type indoor navigation for intelligent robotic wheelchair (TW, US)

Under review

Sensing handlebar for intelligent robotic wheelchair and method for the same (TW, US)

In the next stage, a long-term field test in a nursing home will be also conducted to obtain feedback on the functionality and usability of the iRW or technology modules. In the mean time, the complete function test for each technology module of the iRW will be conducted to confirm the efficacy and reliability. We will be looking for opportunities for technology transfer of iRW, as well as the individual technology module to related companies. Providing a real iRW product which can really assist older adults in daily living has always been our utmost objective.