**2. By-wire conversion**

The conventional wheelchair used in this work is a standard differential drive platform with 2 × 500 W electric motors and a 24 V-40 Ah lead acid battery. Its weight (without person) is 80 kg with the dimensions of 120 cm × 65cm × 100cm. After some effort, now it is able to be driven by the outputs of the autonomy algorithms. **Figure 1** shows the conventional version of the wheelchair which is controlled by a joystick.

The original electric motor driver on this wheelchair is communicating with the joystick via a non-standard protocol, and it was a black box for us since there is no information about how it operates. For this reason, as a first step toward a

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it successfully.

*Conversion of a Conventional Wheelchair into an Autonomous Personal Transportation Testbed*

full autonomy, the motor drivers should be replaced by another one that is able to communicate via a standard protocol and well documented. Therefore, we replaced the motor driver of each motor with a standard brushed DC motor driver "Roboteq MDC2230," which is a dual channel driver and is able to provide 50 A current

In robotic applications, electric motors are generally used in "velocity control mode" instead of "torque mode." For this reason, the motor driver needs to get the actual velocity value as a reference signal to be tracked. Hence, it is mandatory to measure the motor velocity for a feedback controller. For this reason, additional encoders (Atek-ARCB50360HPL33MY8FZ) for each electric motor are included to the system. The joystick is also removed since it is not necessary anymore in the autonomous concept. As a result, we mounted a motor driver that includes two separated drivers in the same box and two encoders. The motor driver box and one

According to the motor driver's data interface, the driver is able to communicate via serial port, which is suitable for our computational system. Since it is planned to use the robot operating system (ROS) [15] to develop and implement the autonomous algorithms, a ROS node is also written to convert ROS commands to serial port data packages using "Rosserial." Rosserial is a protocol for wrapping standard ROS serialized messages and multiplexing multiple topics and services over serial port. As a result, by mounting additional components (two motor drivers and two encoders) and writing a ROS node, the wheelchair is converted to a drive-by-wire system, which means it can take reference velocity commands from ROS and applies

Finally, we added an on-off button in order to open and shut down the whole system. In addition, an emergency button is mounted near the seat to be reached by the human easily. The emergency button is connected to the appropriate input of the motor driver which cuts down the energy to motors immediately when emergency signal comes. The on-off and emergency buttons are shown in **Figure 2**.

*DOI: http://dx.doi.org/10.5772/intechopen.93117*

continuously for each channel.

*Conventional electric wheelchair used as a base system for conversion.*

**Figure 1.**

of the encoders are shown in **Figure 2**.

*Conversion of a Conventional Wheelchair into an Autonomous Personal Transportation Testbed DOI: http://dx.doi.org/10.5772/intechopen.93117*

**Figure 1.** *Conventional electric wheelchair used as a base system for conversion.*

full autonomy, the motor drivers should be replaced by another one that is able to communicate via a standard protocol and well documented. Therefore, we replaced the motor driver of each motor with a standard brushed DC motor driver "Roboteq MDC2230," which is a dual channel driver and is able to provide 50 A current continuously for each channel.

In robotic applications, electric motors are generally used in "velocity control mode" instead of "torque mode." For this reason, the motor driver needs to get the actual velocity value as a reference signal to be tracked. Hence, it is mandatory to measure the motor velocity for a feedback controller. For this reason, additional encoders (Atek-ARCB50360HPL33MY8FZ) for each electric motor are included to the system. The joystick is also removed since it is not necessary anymore in the autonomous concept. As a result, we mounted a motor driver that includes two separated drivers in the same box and two encoders. The motor driver box and one of the encoders are shown in **Figure 2**.

According to the motor driver's data interface, the driver is able to communicate via serial port, which is suitable for our computational system. Since it is planned to use the robot operating system (ROS) [15] to develop and implement the autonomous algorithms, a ROS node is also written to convert ROS commands to serial port data packages using "Rosserial." Rosserial is a protocol for wrapping standard ROS serialized messages and multiplexing multiple topics and services over serial port. As a result, by mounting additional components (two motor drivers and two encoders) and writing a ROS node, the wheelchair is converted to a drive-by-wire system, which means it can take reference velocity commands from ROS and applies it successfully.

Finally, we added an on-off button in order to open and shut down the whole system. In addition, an emergency button is mounted near the seat to be reached by the human easily. The emergency button is connected to the appropriate input of the motor driver which cuts down the energy to motors immediately when emergency signal comes. The on-off and emergency buttons are shown in **Figure 2**.

*Service Robotics*

and tracking.

**2. By-wire conversion**

controlled by a joystick.

Autonomous traveling is possible and a serious need, not only in the way that passenger cars perform in traffic, but also in closed environments where the use of Global Positioning System (GPS) is not possible and where the density of people is high. People may prefer to go somewhere autonomously in a closed environment even if there is no walking disability. Wheelchairs are very suitable vehicles for this kind of personal transportation. Also, for some people with disabilities, wheelchairs are the only option to get from one place to another. Unfortunately, many people with disabilities lack the ability to safely use their wheelchairs. This situation poses serious risks for them, primarily for the people around them and other environmental elements. In line with all these needs, in this paper, design and development

In literature, single-person autonomous/semi-autonomous vehicle studies are generally carried out on the wheelchair platform. The wheelchair named TetraNauta in [5] was developed at the University of Seville between 1998 and 2004, and it operates in a known map autonomously. The study shown in [6] explains the smart wheelchair project that started in 2004 at the Massachusetts Institute of Technology. In this study, an efficient, socially acceptable autonomous tourfollowing behavior was developed. In another work about autonomous wheelchairs [7], RGB-D camera was used as the main perception sensor, and the map of the environment is constructed from this. Ref. [8] provides information on the development of a robot operating point (ROS)-based autonomous wheelchair that will work indoors. Ref. [9] mentions an autonomous wheelchair that uses only light detection and ranging (LIDAR) as its environmental measurement unit. This study is carried out using the ROS platform. In [10, 11], a semi-autonomous wheelchair was designed where the chair was controlled via head movements. In [12], the aim is to estimate the chair pose from video data by using machine learning methods using artificial neural networks. Another autonomous wheelchair study [12] provides the results about navigation in cluttered environments without explicit object detection

All these studies use autonomous/semi-autonomous wheelchairs, which are converted from a conventional wheelchair platform. They provide information about their wheelchairs' autonomy but not deep information about the conversion itself. The conversion process of autonomous systems is explained in some papers for autonomous automobiles [13, 14] but not very detailed for wheelchairs. The dimensions, velocity capabilities, and differential drive architecture make wheelchairs different than standard automobiles. In this paper, we explain how to convert a conventional wheelchair into an autonomous one which is aimed to be used as a testbed for advanced autonomous algorithms. Besides, the results of localizing and mapping algorithms applied on this testbed are illustrated at the end of the work.

The conventional wheelchair used in this work is a standard differential drive platform with 2 × 500 W electric motors and a 24 V-40 Ah lead acid battery. Its weight (without person) is 80 kg with the dimensions of 120 cm × 65cm × 100cm. After some effort, now it is able to be driven by the outputs of the autonomy algorithms. **Figure 1** shows the conventional version of the wheelchair which is

The original electric motor driver on this wheelchair is communicating with the joystick via a non-standard protocol, and it was a black box for us since there is no information about how it operates. For this reason, as a first step toward a

of a fully autonomous smart wheelchair is explained.

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**Figure 2.** *Motor driver, encoder, on-off, and emergency buttons mounted.*
