Using CompactRIO and LabVIEW to Develop Zero-Energy Bus Stop Information Centers


"Using NI hardware and software, we created the world’s first working prototype of a zero-energy bus node."

- K.Z. Tang, National University of Singapore

The Challenge:
Improving our urban infrastructure by designing bus stop information centers that are self-sustainable in energy consumption and user friendly for all commuters, including those with special needs.

The Solution:
Using NI CompactRIO hardware and LabVIEW software to create a bus stop interface with a zero-energy goal (100 percent self-sustainable electricity consumption) that provides intuitive, updated traffic information to passengers and drivers and can serve as a platform for energy grid control.

K.Z. Tang - National University of Singapore
S. Tang - National Universtiy of Singapore
S. Krishnan - National University of Singapore
B. Li - National University of Singapore


Recent technology advances can deliver real-time traffic information across many platforms. There is an urgent need to organize this traffic information so it is relevant for different types of commuters and road users. We need better integration of traffic infrastructures, commuters, and vehicles within the traffic network structure. The bus stop (also called a bus node) is an important infrastructural component in a traffic network that consists of traffic lights, motorways, lamp posts, and road signs, as well as commuters and vehicles.

Bus stops in Singapore do not have features for energy monitoring and control. Less than five percent of bus stops have solar panels installed to provide partial electricity. A fully self-sustainable bus stop is critical in realizing a zero-energy, green-structure concept. Currently, traffic infrastructures, road users, and vehicles are considered discrete components in the whole system. The availability of useful traffic information for road users is in the preliminary stage. Better organization and easier availability of this information can improve the whole travelling experience for all categories of passengers.

Using NI hardware and software, we created the world’s first working prototype of a zero-energy bus node. We developed intelligent bus nodes that can interact with road users and provide useful traffic information in a timely manner. Furthermore, we used assistive technologies to transform such traffic information into audio, video, and other cognitive forms for aged and handicapped users. The system we created also monitors energy consumption at the bus nodes. We incorporated green technologies to improve the energy efficiencies of the bus nodes and nearby facilities. We incorporated special functions at the bus nodes to assist the aged, the handicapped, and school children in using these traffic infrastructures.

Hardware Architecture

The overall schematic diagram of the zero-energy bus node is shown in Figure 1. For this architecture, we used concepts of green technology, cloud computing, and decentralized control. We wanted to make the bus node energy efficient by fully retrofitting it with green structure design features and technologies.

The bus node is a single point in an intelligent traffic network. With an embedded controller, GPS enabled capability, and wireless capability, passengers can obtain the arrival times of the various buses, current traffic conditions, and other useful navigation information on-site at the bus node, without additional devices. Conventionally, passengers obtain current traffic information through a connection to a remote central server and the information is usually obtained from a fixed time schedule. This intelligent bus node performs better than the conventional method. Using a decentralized control structure, the embedded controller communicates with nearby bus nodes and provides accurate, updated traffic information on-site at the bus node. The zero-energy bus node we created is about 40 percent more efficient than a typical bus stop and is self-sustainable in energy consumption.

Energy Harvesting Using Rotational Solar Panel

To achieve net zero-energy power consumption, the bus node must produce its own electricity. This is done through solar panels situated on top of the bus node, covering an area of about 3.5 m by 2.8 m (see Figure 2). In a generally sunny place like Singapore, solar energy is in great supply more than 99 percent of the time. By tapping into this energy, we can provide all the electricity requirements of a single bus node.

To maximize the efficiency of the solar panel, we mount it on a rotational base. Taking into consideration the geographical and other physical constraints at the location of the bus node, we can use the base to tilt the angular position of the panel for maximum efficiency. Updated weather conditions from the local meteorological station are also periodically sent to the embedded controller to control the panel’s angular tilt. To further improve the energy harvesting capability of the panel, we applied a polymer type sticker to the solar panel to bend the incoming sunlight within the glass panel.

Environmental Control Using a Mini Weather Monitoring Station

To minimize electrical energy usage, we mounted a mini weather monitoring station that uses about 250 W of electricity at the bus node (see Figure 3). This station includes sensors for localized temperature, O2, CO2, and H2O (that is, Nose 3 Model NA-3000 sensor and OS-1 oxygen sensor). With these feedback signals, a CompactRIO controller regulates the air circulation at the bus node via the speed-regulating fan that uses about 200 W of electricity and the mirror-paneled glass top that uses about 50 W of electricity (see Figure 4).

Furthermore, we embedded versatile, ultra-thin piezoresistive force sensors below the cement platform of the bus node (see Figure 5), which determines the level of crowdedness. The control actions regulating the fan speed and the rooftop glass panel are determined by the fuzzy controller embedded within the CompactRIO. Energy-saving light tubes that use about 22 W of electricity provide lighting conditions at the bus nodes (see Figure 6). Photodetectors at the bus node provide the daylight conditions, then the embedded controller determines when to turn on the light tubes.

Assistive Technologies

The bus node also includes assistive technologies in the form of audio, video, and other cognitive formats for passengers with special needs such as the elderly, school children, and the handicapped. Besides providing updated traffic information for the passengers at the bus node, approaching bus drivers are also alerted of important traffic information. This traffic information is mounted in the direction of the approaching bus drivers. Radio frequency identification (RFID) receivers are mounted at the bus node. When a special needs passenger wearing or holding an RFID tag is at the bus stop, the embedded controller provides an intuitive message for the approaching bus driver.

The message that flashes to the bus driver depends on the type of tag sensed by the controller. For example, if an elderly person is at the bus node, the message would flash “An elderly person is at bus node.” The message to alert the bus driver of handicapped passengers wanting to board the bus would be “Handicapped help needed.” The RFID tag can easily be embedded on the boarding ticket of these special needs passengers. The cards must conform to the new Singapore standard for Contactless ePurse Applications (CEPAS).

In addition, for special needs passengers requiring other cognitive forms of traffic information, the system provides a digital speaker and an intuitive screen. The digital speaker announces the arrivals of buses at the bus node to help visually impaired passengers to board the correct bus. For hearing impaired passengers, the intuitive screen highlights the updated bus information.

As the bus node is a point of energy consumption and harvesting, the grid control of the bus node network is managed using green technologies for energy harvesting, monitoring, and distribution.

Software Architecture

The entire system we created is divided into three main functioning blocks: the sensors, the controller, and the actuator. We built the control system using CompactRIO and LabVIEW system design software. For the processor to interface with the external sensors and actuators, the NI cRIO-9215 module, NI 9263 module, and NI cRIO-9401 module obtain and produce the analog and digital control signals. We built VIs on the real-time (see Figure 7) and FPGA (see Figure 8) targets on the controller platform. The fuzzy inference machine runs on the real-time platform.


With integrated hardware and software from NI, we seamlessly created a network of decentralized, controlled bus nodes with embedded assistive technology for young, elderly, and handicapped passengers. The zero-energy bus node is 100 percent self-sustainable in electricity consumption, yet provides intuitive and updated traffic information for passengers and drivers. Furthermore, the network of bus nodes serves as a ready platform for energy grid control activities such as energy monitoring and harvesting.

Author Information:
K.Z. Tang
National University of Singapore
EA, #07-26, 9 Engineering Drive 1
Tel: 65 164460
Fax: 67 773117

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