ISA MOTORBIKE

A speed-controlled motorcycle was also developed as part of the ISA UK trials.

The base vehicle for ISA Motorbike was a Suzuki Bandit 650s (see Figure 1). The Bandit was chosen because of its reputation as an easy-to-ride bike and that it is a suitable size for both men and women to ride. This partially-faired bike was also chosen because of the easy access to the engine and the potential space for modifications. A top box was added to the bike for additional storage of the ISA components.

Figure 1 – Suzuki Bandit 650s

A very different approach was taken to the ISA motorbike, compared to that of the ISA Car. This is due to the unique nature of the motorbike and the fact that its speed and stability are intrinsically linked. By affecting the speed of the bike with the ISA system there were concerns that the vehicle’s stability could be adversely affected. It was important that any changes the ISA system would implement to the bike should be smooth and in no way put the rider in danger. With these problems in mind the ISA Motorbike system was developed with a philosophy of “Heavy Persuasion, Moderate Intervention” unlike the strict control used in the ISA Car.

As part of this “Heavy Persuasion” the ISA Motorbike enters a state of warning, where the rider is informed, using various alerts, that the bike is exceeding the speed limit. If the rider chooses to ignore the ISA warnings only then an intervention with the vehicles speed will occur.

ISA MOTORBIKE IMPLEMENTATION

The ISA Motorbike system, unlike the ISA Car, has it own CAN, or Control Area Network. CAN is a standardised protocol for sending and requesting of information on a serial bus system.

A number of stand-alone modules are connected to form the ISA Motorbike CAN (see Figure 2). All the modules can receive or transmit information onto the network. Individual modules interpret the signal from the CPU and set in motion the appropriate response.

Figure 2 - Overview of ISA Motorbike CAN

LOCATION

The motorbike’s location, like that of the ISA Car, is determined using GPS. The GPS signal is detected by a GPS aerial and the GPS module determines the longitude, latitude, heading and speed of the bike. The information from the GPS module is put onto the CAN and can be detected by all the system modules

Unlike the ISA Car and Truck the ISA Motorbike doesn’t use a map to identify the position of changes in speed limit. Instead the system on the motorbike uses GPS virtual beacons to locate changes in speed limit. A virtual beacon is a circular zone of influence, of a given diameter, whose centre is defined by its latitude and longitude (see Figure 3).

Figure 3 - Diagram of a Virtual Beacon

Each virtual beacon has a designated speed limit that corresponds to an existing speed limit on the motorbike’s route. The PDA, within the PDA module, contains a look-aside table that defines the latitude and longitude, speed limit, heading (+/-10o) and the name of each virtual beacon.

If the motorbike’s longitude and latitude are within the area defined by the virtual beacon’s zone of influence and within the specified heading the beacon is said to be “true” and the system implements the new speed limit. The ISA system will continue to assume the last known speed limit is true until it passes through the next virtual beacon (see Figure 4).

Figure 4 – How a vehicle identifies uses virtual beacons to

identify new speed limits

Because the ISA Motorbike uses a virtual beacon system to identify the speed limits it doesn’t have the look-ahead functionality of the ISA Car. The Bike does not know what the new limit will be until it enters the next true beacon and is unaware what the future speed limit will be. This becomes apparent when the bike is travelling from a high speed limit to a low speed limit, or vice versa.

For example, if a rider was travelling at 60mph in a 60 speed limit approaching a 30 limit and not slowing down the ISA motorbike would only be able to Intervene and reduce the vehicle’s speed once it was within the zone of influence of the new virtual beacon. The motorbike would only start to decelerate as it entered the 30 limit and, therefore, would be travelling faster than the 30 mph for some time as it entered the new limit.

This issue highlights the importance of the virtual beacon’s location. To reduce this overshooting of the speed limit it is important to locate the beacons slightly before the speed limit sign, although the same affect can be achieved by increasing the zone of influence of virtual beacon’s with a large change in speed.

Another difference between the location system used on the ISA Motorbike and that used on the ISA Truck and Car is the fact that the virtual beacon system relies solely only GPS. Unlike the other ISA systems, which use Dead Reckoning to check the vehicle’s location, the ISA Motorbike is vulnerable to the unpredictability of the satellite signal due to the topography of the area.

Interpretation and Command

Unlike the other ISA vehicles the ISA Motorbike reacts differently depending on the extent to which the rider exceeds the speed limit. The ISA Motorbike’s behaviour can be divided into 3 different states:

1. ISA Non-Intervention, when the bike is below the speed limit.
2. ISA Warning, when the bike has slightly exceeded the speed limit.
3. ISA Intervention, when the bike has significantly exceeded the speed limit.

The speed condition under which the ISA Motorbike enters these states is defined in a look-aside table on the PDA (see Table 1).

Table 1 – A Look aside table for Warning and Power-Down Limits

on the ISA Motorbike

If the motorbike’s speed is less than the Warning limit for the given speed limit, for example 53 in a 50, the bike will stay in the “Non-Intervention” state.

If the motorbike’s speed is more than the Warning Limit but less than the Intervention Limit, for example 56 in a 50, the bike will enter the “Warning” state.

If the motorbike’s speed is higher than the Intervention Limit, for example 60 in a 50, the bike will enter the “ISA Intervention” state.

When the PDA module on the ISA Motorbike recognises a true virtual beacon it compares the actual vehicle speed to the speed limit for that beacon. Once it has determined what state the motorbike is in (either Non-Intervention, Warning, or Intervention) the PDA module publishes it onto the CAN bus. All the ISA Motorbike sub-system modules have the capability to receive messages on CAN Bus and are aware of what state the bike is in. Individual modules then interpret and command their own responses, depending on what state the vehicle is in.

The PDA also logs the longitude, latitude, heading, vehicle speed and beacon name at a rate of 10 Hz onto a Secure Digital Disk. The data collected is used in the analysis of trial data.

System Monitoring

Similarly to the ISA Car the ISA Motorbike monitors the rider’s requests to disable the system (see ISA MOTORBIKE HMI for methods of disabling the ISA system).

CONTROL

The ISA system on the motorbike uses a reduction in throttle demand to slow the vehicle down. Due to the vehicle’s inherent lack of stability no modifications were made to the motorbike’s brakes.

Within the Servo module is a servo motor (see Figure 5) that is used to limit the motorbike’s throttle. The servo motor arm is connected to a cable that is attached to the throttle return limb. The servo motor’s range of motion is equivalent to the range of motion of the motorcycle twist grip.

Figure 5 - The servo motor usedto limit the ISA motorbikes throttle

The Mulitiplex Rhino Digi 4

When the ISA Motorbike enters the Intervention state the servo is activated the arm rotates, over two seconds, through its range of motion. This rotation pulls the throttle return limb back, closing the throttle and slowing the motorbike down. As the throttle return limb closes the rider feels the twist grip close in their hand. The throttle will remain closed until the motorbike’s speed is below the Warning speed limit.

When the bike is below the warning limit the servo arm rotates back, over two seconds, through its range and the rider regains control of the throttle. The bike returns to the Non-Intervention state.

ISA MOTORBIKE HMI

The HMI used on the ISA Motorbike is similar to that used on the ISA Car and Truck. The speed limit is displayed on a screen (see Figure 19) located in front of the rider on the handlebars and the change of speed limit is punctuated by audio alerts (the rider is required to wear earphones connected to the ISA Motorbike system in order to listen to the system alerts).

Figure 1 – ISA Information Screen

As described previously in ISA Motorbike - Interpretation and Command, the ISA Motorbike is unique from the other ISA systems because it has both and Intervention and Warning State. The ISA Motorbike has a philosophy of “Heavy Persuasion, Mild Intervention” unlike the more strict control of the ISA Car and Truck. This means the rider is aggressively warned, using various methods to alert the rider, before any intervention takes places.

During the Warning phase, when the vehicle is slightly above the speed limit, the following inputs are supplied to the rider:

• The rider will see the warning lights mounted on the screen flash intermittently.
• The rider will feel the shaker located in the saddle pulse intermittently.
• The rider will hear a slow beeping audio alert.

If the ISA Motorbike enters the Intervention phase, when the vehicle has significantly exceeded the speed limit, the following inputs are supplied to the rider:

• The rider will see the warning lights mounted on the screen flash quickly.
• The rider will feel the shaker located in the saddle pulse quickly.
• The rider will hear a fast beeping audio alert.
• The rider will feel the twist grip roll closed as the power of the vehicle is reduced by the actuator.

Figure 6 – The ISA Motorbike system elements

The rider can be temporarily exempt or permanently disable the ISA Motorbike system using the Opt-Out and Emergency Override buttons (see Figure 6), which operate in a similar way to the buttons on the ISA Car and Truck.