Autonomous mobility scooter requirements

To go back to the mainpage: PRE2017 3 Groep6.

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in order to make a product or a model of the system, it must first be decided what the actual requirements and limitations of our model are. with these requirements we can see what our model should eventually do.

we have split the requirements in four different sections, to split main concerns of the system.

navigation: these requirements concern everything to with the software and navigation, what it should, can, cannot or should not do.
safety: these requirements concern safety issues of a mobility scooter.
smart mobility: these requirements concern how to enhance the mobility scooter such that it responds to the requests of the user.
physical: these requirements concern the actual hardware that is needed for the mobility scooter.

navigation

1. the mobility scooter can navigate through a shop.
2. the mobility scooter can use elevators.
3. the mobility scooter can use public transport.
4. when the mobility scooter encounters an obstruction, the mobility scooter will alter it's path to go around the obstruction.
5. the mobility scooter will offer up to three alternative paths to the destination.
6. the mobility scooter can navigate regardless of the lightlevel
7. the mobility scooter can navigate when it is raining
8. the mobility scooter can navigate through fog, when visibility is less than 50 meters
9. the mobility scooter can drive through snow less than 5 cm deep.
10. the mobility scooter can differentiate between a road and a cycle path.
11. when the mobility scooter encounters a trafficlight, the mobility scooter can determine which light of the trafficlight is on

safety

1. The mobility scooter can not drive faster then 6 km/h on a walking path.
2. the mobility scooter should not get closer than 10 centimetres to another person while driving.
3. if the autonomous system detects a failure, it notifies the user through the use of sound.
4. The mobility scooter can detect change in height in the road ahead. (curbs, speedbumps, holes, ramps)
5. The mobility scooter can detect a berm.
6. The mobility scooter can detect Bushes.
7. The mobility scooter can detect Cyclists.
8. The mobility scooter can detect pedestrians.
9. The mobility scooter can detect animals.
10. The mobility scooter can detect motorised vehicles.
11. The mobility scooter will not fall over.
12. The driver of the mobility scooter can not fall out of the scooter.
13. The mobility scooter should allow the driver to intervene, if they don't trust the scooter.
14. The mobility scooter should not cause bodily harm when a failure occurs.
15. The mobility scooter should notify the user through the use of sound and visual display when the sensors are blocked. (Also UI related)
16. The mobility scooter can safely move to a safe spot when the battery is less than 10% full.
<- what is safe?
17. The mobility scooter can safely operate with a driver of up to 125kg.
18. The mobility scooter will stop moving if the driver falls out.
19. The mobility scooter will give auditory and visual feedback if a wheel has been blocked.
20. The mobility scooter can override the driver input when collision is imminent. (Not unusual that the applies the accelerator when trying to brake. Another example is that the driver wants to go forward but the scooter is in reverse)
21. Will not tilt and fall when driving on a surface with a slope of more than 10° "(ratio 1:5)".
22. The mobility scooter can not drive if there is no driver on the mobility scooter

smart mobility

1. The mobility scooter has a display.
2. The mobility scooter has a speaker system
3. The scooter allows the user to set their destination using the display.
4. The scooter allows the user to set their destination using voice commands.
5. The scooter allows the user to alter communicative and other settings, such as favorite destinations. <- this requirement needs to be looked at and be more specific
6. The scooter allows a user to get in using up to x seconds. time to be edited after more research
7. The scooter provides auditory feedback to the user.
8. The scooter provides visual feedback to the user.
9. The scooter can 'warn' people in vicinity of the scooter
10. The scooter can be controlled through the use of either a steering wheel, a joystick or voice commands.
11. The scooter can connect to the user's smartphone.
12. The scooter maintains a connection to the internet.
13. A user can make calls with the scooter.
14. A user can send texts with the scooter.
15. The scooter can self
16. initiate a call in case of an emergency.
17. The scooter can communicate with other scooters to gather and share sensory information in their environment.

physical

1. the mobility scooter should have batteries that can last 3 hours of driving time
2. the mobility scooter should have a computer system built in such that it can process the massive amount of data
3. the mobility scooter should have wireless communication to other vehicles
4. the mobility scooter should have wireless communication with a server
5. The autonomous mobility soocter will have flashing lights.
6. The autonomous mobility scooter will have whit front lights.
7. The autonomouw mobility soocter will have red back light.
8. The mobility scooter through a standard door (dimensions to be added)

legal requirements

1. The mobility scooter will not drive faster than 6km/h on a side walk
2. The mobility scooter will not drive faster than the speed limit when on a bicycle path
3. The mobility scooter will not drive faster than 30 km/h on a bicycle path inside the built
4. up area.
5. The mobility scooter will not drive faster than 40 km/h on a bicycle path outside the built
6. up area.
7. The mobility scooter will not drive faster than 45 km/h on a regular road.
8. The mobility scooter will not drive faster than the speed limit when on a regular road.
9. When driving on a bicycle path the autonomous mobility scooter will not drive next to an other mobility scooter.
10. When driving on a regular road the autonomous mobility scooter will not drive next to an other mobility scooter.
11. When driving on a sideway the mobility scooter will obey the right of way rules for pedestrians.
    
12. When driving on a bicycle path the mobility scooter will follow the right of way rules for mopeds.
13. When driging on a regular road the mobility scooter will follow the right of way rules for mopeds.
14. The mobility scooter will use flashing lights when changing driving directions.
15. The mobility scooter will have his light on between 30 minutes before sunset and 30 minutes after sunrise when it is being used.
    
16. The mobility scooter will ahve its light on during bad weather when it is used.

reasoning

navigation

1. As many of the incidents are caused inside shops, and people get stuck in shops sometimes, we believe this is a necessary requirement to add [1]
2. As a mobility scooter cant use escalators or stairs, there will often be a situation where it would have to take the lift
3. A user of a mobility scooter often cant travel far because they rely on their mobility scooter. If they are able to use public transport, they arent limited by the range of their mobility scooter
4. this is trivial for autonomous driving systems[1]
5. a user may want to take alternative routes to a destination to take a more scenic route. [1]
6. the mobility scooter should still be able to navigate itself when in a dark room, or outside when its dark. this would mean that the mobility scooter cant simply rely on normal cameras.
7. if its raining, the sensors should not be able to be obstructed by the rain this is necessary for the choice of sensors and where to place them
8. if it is foggy, the sensors should not be able to be obstructed by the fog this is necessary for the choice of sensors
9. if there is only a small amount of snow, a mobility scooter user should still be able to go outdoors and do their usual stuff. especially since mobility scooter users are less mobile, a small amount of snow would block them from going outside as it can be slippery, but with the mobility scooter they could still go out and get food etc.
10. the mobility scooter should differentiate between a road and a cycle path such that it knows where it has to drive, and what kind of obstacles there are.
11. as the mobility scooter can encounter quite a few traffic lights when driving towards the destination, it is necessary that the autonomous vehicle can read and understand traffic lights.

[1] = user scenario

safety

1. the mobility should not cause danger for the user or the other road users
2. the mobility scooter should keep a safe distance from other people to avoid collision
3. if there is an error in the system, it should notify the user somehow, we believe he best way of doing this is through using sounds. this does however need more research.
4. the mobility scooter should have the ability to see bumps and holes in the road to make sure it goes over them safely.
5. part of the autonomous system to see the side of the road
6. part of the autonomous system to see the side of the road
7. part of the autonomous system to detect obstacles
8. part of the autonomous system to detect obstacles
9. part of the autonomous system to detect obstacles
10. part of the autonomous system to detect obstacles
11. trivial
12. the mobility scooter shouldnt be able to cause the user any harm, and prevent it when possible
13. in case of the scooter making a mistake without detecting it, the user should always be able to take over
14. the mobility scooter shouldnt be able to cause the user any harm, and prevent it when possible
15. if sensors are blocked, it should notify the user such that the user can make sure nothing goes wrong
16. if the battery would suddenly die, the user would get stranded
17. if the driver is too heavy, braking is alot more difficult, and would have a high chance of crashing into an obstacle
18. stopping the vehicle would prevent any more injuries as the vehicle could just drive on since its autonomous
19. to notify the user that there is something wrong with the scooter and the user can act correspondingly
20. similar to what cars have these days, if a collision is imminent, the vehicle would brake in any case to minimise any possible injuries
21. the mobility scooter shouldnt be able to cause the user any harm, and prevent it when possible.
22. similarly to a driver falling off the mobility scooter, to prevent any injuries caused by a self driving vehicle not having a driver to make sure everything goes alright

Solutions

Safety

Staying seated

The mobility scooter has to have a seatbelt and armrests to prevent the driver from falling out of the scooter when doing any sort of maneuver that does not necessarily result in the scooter falling. (12)

For extra safety the scooter should be able to detect if the seatbelt is being used and prevent driving when the seatbelt is not being used to further reduce the change of the driver falling out of the scooter. This could be done with a detection system in buckle of the seatbelt. ( Note that the user could insert the seatbelt in the buckle before getting seated. In this case this system would think that the driver has used the seatbelt, while that’s not the case.)

By adding a weight sensor in the mobility scooter, the scooter can detect if a driver is seated in the mobility scooter. If for any reason the driver falls out of the scooter, the weight sensor can detects it and act accordingly (stop moving). (18) The sensor should have a minimum weight it has to detect before the system concludes that the driver is present. The scooter should not think that the driver is present when, for example heavy groceries are placed on the seat and drive of without the passenger if the drive command is given accidently. If this limit is 30 kg, most objects placed on the seat should not activate the sensors, while it will engage if a person is seated. (22)

Stability

To minimize the chances of the entire scooter from falling the scooter has to be stable. In the research group of VeiligheidNL 94% of the people injured were using a mobility scooter with three wheels, the reaming 6% was using a mobility scooter with four wheels. Therefore the scooter should have 4 wheels. In most cases the accident occurred through an height difference between the wheels. Making sure the center of gravity of the scooter is as low as possible and as centered as possible, will make the mobility scooter more stable. Lowering the center of gravity also means that the scooter will be less likely to fall when driving on a sloped surface. (11, 21) ( This is something important to keep in mind when mounting extra equipment onto the mobility scooter)

Intervention

For the driver to be able to override the what the scooter is doing. The scooter should be able to detect when the driver is trying to override. The driver can steer in a different direction, brake, accelerate and/or change to reverse. Any of these actions can be done on purpose or by accident and any combination is possible.

All this while the scooter should also be able to take over from the driver when the driver makes a mistake.

( This is a complex topic, further exploration necessary. The combination of the driver being able to correct the scooter and the scooter being able to correct the driver can create a loop.) (13, 20)