//Logo Image
Authors: Yeh-Liang Hsu, Po-Er Hsu, Yi-Shin Chen (2010-08-21); recommended: Yeh-Liang Hsu (2010-08-21).
Note: This paper is presented at the 25th World Electric Vehicle Symposium and Exposition (EVS 25), Nov 5-9, 2010, Shenzhen, China.

Development of an intelligent robotic wheelchair as the center of mobility, everyday living, and healthcare of the senior users

Abstract

This paper describe the design concept and current progress of an intelligent robotic wheelchair (iRW) developed at he Gerontechnology Research Center of Yuan Ze University, Taiwan, which intends to redefine the wheelchair as the center of mobility, everyday living and healthcare of the senior users. Centered on the needs of the senior users, the core of the iRW is a user interface designed specifically for the senior users’ declining ability in perception, motor control and cognition. The iRW is composed of a moving vehicle, a sensing and control module, and an information/communication module, to provide the senior users three types of functions: mobility, everyday living, and healthcare. The iRW is expected to assist the senior users to interact with the environment more effectively, including physical interaction, environmental control, information exchange, and most importantly, interpersonal communication. The final aim is to enhance independence and social participation, and to improve the quality of life of the senior users.

Keywords: robotic wheelchair, Mecanum wheel, indoor navigation, home telehealth system, Stewart platform.

1.    Introduction

The rapidly aging society has brought an increasing demand in living support and healthcare. Social participation of the elderly people is also becoming an issue of increasingly concern. Lower limb disability is one of the most common disabilities among elders, and wheelchair is the most common and important mobility aids. Electrical wheelchair is an option for senior users who cannot move themselves on a wheelchair. However, operating an electrical wheelchair is often difficult for senior users. Fehr et al. [1] surveyed 200 people with severe disabilities who were trained for operating electrical wheelchairs. Ten percent of the testers thought electrical wheelchairs cannot satisfy their living requirement and 40 percent could not use electrical wheelchairs to move to where they wanted. Although this survey is for disable people, the usability of electrical wheelchairs can also a major problem for senior users.

In recent years, research in electrical wheelchairs has been emphasizing on how to implement the sensing and judgment capabilities commonly seen on robots, so that the wheelchairs can perform autonomous behaviors to a certain extent in order to improve its usability. Miller and Slack [2] first used the term “robotic wheelchair” in their research. They applied various sensing and navigation technologies that are often used in robotics and built two prototypes of robotic wheelchairs, which were able to assist users to pass through narrow paths and avoid obstacles.

Automatic navigation is one of the major research issues in robotic wheelchair, since mobility assist is the fundamental function of a wheelchair. Prassler et al. [3] developed robotic wheelchair MAid (Mobility Aid for Elderly and Disabled People) to support and transport senior users with limited motion skills and to provide them with a certain amount of autonomy and independence. As shown in Figure 1, in a test, MAid could travel autonomously in the concourse of a railway station through crowded people.

Figure 1. Robotic wheelchair MAid, traveling in the concourse of a railway station [3]

Besides navigation, man-machine collaborative control scheme is also a very important issue of the research of robotic wheelchair [4, 5]. Galindo et al. [6] developed a robotic wheelchair SENA to facilitate mobility of the disable people and senior users. They considered completely autonomous performance of a mobile robot within non-controlled and dynamic environments is not possible yet, due to different reasons including environment uncertainty, sensor/software robustness, limited robotic abilities, etc. They presented the design and implementation of the human-robot-integration idea into SENA, which permits a person to extend/improve the autonomy of the whole system by participating at all levels of the robot operation, from deliberating a plan to executing and controlling it. Figure 2 shows the execution of navigation tasks from interactions between human and robotic wheelchair

Figure 2. Executions of navigation tasks from interactions between human and robotic wheelchair [6]

Bourhis and Agostini [7] considered collaboration between the users and robotic wheelchairs will improve the efficiency of navigation tasks. They classified the collaborative relationship into behavior model, man supervisor, and robot supervisor, and implemented the collaborative control strategy in their robotic wheelchair VAHM. Takahashi et al. [8] developed a robotic wheelchair in which the user can use body posture to control forward/backward motion by sensing the change of user’s center of gravity (Figure 3). Katsura et al. [4] combined the capability of the user and the robotic wheelchair to design the collaborative scheme to reduce the operational load for the user.

Figure 3. Use the change of user’s center of gravity to control robotic wheelchair forward/backward [8]

Observing the elderly people living in nursing home or in the home environment, the wheelchair is the place where they spend the most time in everyday living for many senior users. In addition to providing mobility assistance, the wheelchair should also integrate and satisfy the needs in everyday living, healthcare, and social participation.

This paper describes the design concepts and current progress of an on-going research project conducted in the Gerontechnology Research Center in Yuan Ze University, Taiwan, in constructing an intelligent robotic wheelchair (iRW), which intends to redefine the wheelchair as the center of mobility, everyday living and healthcare of the senior users, based on the concept of robotic wheelchairs. Figure 4 describes the overall design concept of the iRW developed in the study. Centered on the needs of the senior users, the core of the iRW is a user interface designed specifically for the senior users’ declining ability in perception, motor control and cognition, a moving vehicle. The iRW is composed of a moving vehicle, a sensing and control module, and an information/communication module, to provide the senior users three types of functions: mobility, everyday living, and healthcare. The iRW is expected to assist the senior users to interact with the environment more effectively, including physical interaction, environmental control, information exchange, and most importantly, interpersonal communication. The final aim is to enhance independence and social participation, and to improve the quality of life of the senior users.

Figure 4. Design concept of the iRW

2.    Design concept of the iRW

The iRW is currently in the prototyping stage. The functions planned for the iRW are described as follows:

(1)  Mobility

The iRW is designed for home or nursing home use, to be used mostly indoor or short-distance outdoor (such as taking a walk in the garden). The iRW employs a Mecanum-wheeled vehicle which can move in any direction for nimble maneuver. The iRW also shows autonomous behaviors by implementing functions such as the indoor navigation, obstacle avoidance, and dynamic route planning. Schemes of collaborative control are also developed to make the iRW more convenient and easy to use in home and nursing home environments.

(2)  Everyday living

The iRW uses the concept of Stewart platform to design a versatile seat mechanism with multiple degrees of freedom in seat adjustments to provide transfer assist and comfortable seating positions to the senior user to handle the various situations encountered in everyday living. Interacting with the wireless sensor network constructed in the home or nursing home environment, the iRW provides the senior user with convenient environmental control. The information and communication module in the form of a digital photo frame embedded in iRW also provides a channel of information exchange and interpersonal communication for the senior user.

(3)  Healthcare

The iRW provides an easy-to-wear, non-invasive device for blood oxygenation measurement. Other physiological signals such as heart rate and respiration rate can be derived for real time monitoring of the signs of life. Combining with the information and communication module, a home telehealth system is also achieved on the iRW.

Figure 5 is the appearance planned for the iRW. The current progress of the various systems of iRW will be described in the next section.

Figure 5. Appearance planned for the iRW

3.    Mobility assistance

Mobility assistance is the basic function of the robotic wheelchair. Nimble maneuverability is of the highest priority for the iRW to be used in the crowded indoor home environment. For this reason, the moving vehicle of the iRW uses 4 Mecanum-wheels, which was designed by Swiss inventor Bengt Ilon. As shown in Figure 6, the outer ring of the Mecanum wheel has free rollers in a 45 degree angle with the wheel’s axis. The vehicle can move in all directions by controlling the direction of rotation of the 4 Mecanum wheels.

Mecanum wheels have been used in electrical wheelchairs, as shown in Figure 6. In our design, the moving vehicle of iRW can go forward/backward, shift right/left, and rotate clockwise/counterclockwise by controlling a joystick.

Figure 6. The Mecanum wheel and application [http://car.pege.org/2006-ever-monaco/wheel-chair.htm]

We did not implement complete automatic navigation function in the iRW because it is too costly to be practical to achieve the required accuracy. Instead, a semi-autonomous indoor navigation using landmarks is implemented using the concept similar to the automated guided vehicles (AGV) to reduce the operation load of senior users. Landmarks are deployed on the ceilings as “virtual AGV track”. When iRW is steered under a landmark and a camera on the iRW catches and identifies the landmark, the iRW can then interpret the information contained in the landmark and follow the virtual AGV track to move to the specific location, such as bed room, living room, kitchen, etc.

This semi-autonomous indoor navigation system is low cost, flexible, and easy to implement. The QR code (Quick Response code), which is a two-dimensional bar code system commonly used in various applications, is used as to generate the landmarks in this system. There are many software programs for generating and recognizing QR code. The user can generate and print out the QR code landmarks and easily deploy the virtual AGV track in the home environment. For example, Figure 7 shows “bedroom” and “kitchen” in QR code. In addition, ultrasonic range-finding sensors are used to perform the low cost and reliable function of obstacle avoidance. When an obstacle is detected within a specific distance from the iRW, iRW simply stops all autonomous behaviors and handed the control to the user.

Figure 7. “Bed room” and “kitchen” in QR code

4.    Seat adjustment mechanism

The iRW uses the concept of Stewart platform to design a versatile seat mechanism with multiple degrees of freedom in seat adjustments needed in various situations encountered in everyday living, including comfortable seating positions and transfer assists from wheelchair to bed, toilet, etc.

Stewart platform is a parallel structure robot which has the advantages of high stiffness and high positioning accuracy compared to the serial structure robots. The geometry of this parallel robot, illustrated in Figure 8, is composed of a fixed base, a movable platform, and 6 variable length actuators connecting the fixed base and the movable platform. This is a 6 degrees-of-freedom universal-prismatic-spherical mechanism, including heave, surge, sway, yaw, pitch, and roll.

Figure 8. Schematic diagram and degrees-of-freedom of parallel robot

Considering adjustments required in transfer assist and comfortable seating positions, the seat mechanism of iRW needs only 4 degrees-of-freedom which are heave, surge, sway, and pitch. As shown in the conceptual sketch in Figure 9, the seat mechanism of iRW uses a four-axis Stewart platform. In this design concept, the Mecanum-wheeled vehicle is the fixed plate, while the seat is the movable plate of Stewart platform. Based on this design concept, the prototype of the iRW is developed (Figure 10). In order to enhance the stability of the seat, a locking-mechanism is designed to constrained uncontrolled degree of freedoms (surge and sway) of the seat. Table 1 shows the functions and specifications of the seat adjustment mechanism iRW.

Figure 9. Design concept of the seat adjustment mechanism of iRW

Figure 10. Prototype of the iRW

Table 1. Functions and specifications of the iRW

 

Functions

Specification

Adjustment of comfort

Height of the seat

(Distance from the bottom of the seat to the ground)

Highest position: 498mm

Initial position: 433mm

Lowest position: 368mm

Adjustment of assistance

Stand assist

+15°(Pitch)

Back/hip pressure variability

+15° ~ -15°(Pitch)

Transfer assist

130mm (left/right)

5.    Home telehealth system

The home telehealth system of the iRW is in the form of a “Care Delivery Frame (CDF)”. CDF integrates two distinctly different applications, the home telehealth system and the remote photo sharing service of digital photo frame, to create a unique information channel for senior users who are not familiar with the operation of computers and Internet. In addition to health data monitoring, children or caregivers can “deliver care” to their seniors not living together by warm messages and thoughtful reminders on the CDF, as well as sharing their feelings, joy, and life experience through photos and video clips. Even more applications can be imagined once this information channel to the seniors at home is established, such as entertainment, displaying life information or even commercial ads. As shown in Figure 11, CDF provides the following 4 main functions:

(1)     Home telehealth

The basic function of CDF is the Distributed Data Server (DDS) of the decentralized home telehealth system [9]. All technical functions of a home telehealth system are built in the CDF. Currently the vital sign sensors that can be connected to CDF are blood pressure meter, blood glucose meter, and blood oxygenation sensor.

(2)     Remote photo sharing

CDF provides a platform for children and caregivers to upload photos and videos clips remotely, and to manage the display sequence and timing on the CDF for their seniors not living together.

(3)     Caring messages and reminders

Children/caregivers can send warm caring messages and thoughtful reminders to their seniors to display on the CDF.

(4)     Entertainment and life information

Collaborating with information service companies, CDF can also be a platform to display information such as weather, shopping, as well as music and other entertainment information.

Figure 11. The 4 main functions of the Care Delivery Frame

The CDF software is running independely on a “pad PC”, which can be installed and seperated from the iRW when the senior user leaves the iRW. Figure 12 shows the management pages of the 4 main functions for CDF.

   

Figure 12. Management pages of the 4 main functions for CDF

6. Conclusion

Figure 13 shows photos of the first prototype of iRW developed in this project, which is in a skeleton form constructed by aluminum extrusions. This prototype is currently under intensive testing for functions. Human factor evaluations and industrial design are also being carried out. After the functional tests are completed, a field test of the iRW will be conducted in a nursing home to get feed back from the senior users and further improve its usability.

Figure 13. Photos of the first prototype of iRW

Reference

[1]     Fehr L., Edwin Langbein W., Skaar S. B., 2000. “Adequacy of powerwheelchair control interfaces for persons with severe disabilities: Aclinical survey,” J. Rehabil. Res. Develop., v. 37, pp. 353–360.

[2]     Miller, D., Slack, M., 1995. “Design and testing of a low-cost robotic wheelchair prototype,” Autonomous Robots, v. 2, pp. 77-88.

[3]     Prassler, E., Scholz, J., and Fiorini, P., 2001. “A robotics wheelchair for crowded public environment,” Robotics & Automation Magazine, IEEE, v. 8, pp. 38-45.

[4]     Katsura S., Ohnishi K., 2004. “Human cooperative wheelchair for haptic interaction based on dual compliance control,” Industrial Electronics, IEEE Transactions on, v. 51, pp. 221-228.

[5]     Galindo C., Cruz-Martin A., Blanco J.L., Fernández-Madrigal J.A., Gonzalez J., 2006a. “A multi-agent control architecture for a robotic wheelchair,” Applied Bionics & Bionmechanics, v. 3, pp. 179-189.

[6]     Galindo C., Gonzalez, J., Fernández-Madrigal J.A., 2006b. “Control architecture for human–robot integration: application to a robotic wheelchair,” Systems, Man and Cybernetics, Part B, IEEE Transactions on, v. 36, pp. 1053-1067.

[7]     Bourhis G, Agostini Y., 1998. “Man-machine cooperation for the control of an intelligent powered wheelchair,” Journal of Intelligent & Robotic Systems, v. 22, pp. 269-287.

[8]     Takahashi Y., Shinobu Ogawa S., Machida S., 2002. “Mechanical design and control system of robotic wheelchair with inverse pendulum control,” Transactions of the Institute of Measurement and Control, v. 24, pp. 355-368.

[9]     Hsu, Y. L., Yang, C. C., Tsai, T. C., Cheng, C. M., Wu, C. H., 2007. “Development of a decentralized home telehealth monitoring system”, Telemedicine and e-Health, Vol. 13, No.1, pp. 69-78.