Let's Make Robots!

Trolley speed control

Imagine that you want to have a kind of "automated control" for a trolley (i.e. a golf trolley). What kind of automation system would you use?

The basic requirements would be the follwoing ones:

- Trolley is stopped, you push it and it starts due to the force of the push.

- The trolley accelerates in order to reach the speed at which you're walking.

- When the trolley is having the same speed than the person walking behind it the force on the trolley handle is almost nul and the trolley runs at this speed.

- You want to reduce your walking speed and exert a force backward to the trolley motion direction. The trolley reduces its speed.

- If the person is not touching at all the trolley it decelerates and stops.


What do you have in mind to achieve such an automatism? Force / pressure sensors and microcontrollers?

Thanks in anticipation for your ideas!

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@ Antonio

Thanks for your comment. I thought that powered trolley in supermarkets were just having a speed dial and a power on/off button, but not an automated speed control in order to move at the same speed than the operator is walking.

By the way, were you dealing with trolleys used by the supermarket employees or by the customers?

Look at the powered trolleys they use in supermarkets.

They have a handle with an integrated pressure sensor.

The controller of the cart tries to bring the pressure measured by the sensor to zero using a PID controller.

The handle could also include a switch that is closed by squeezing the handle bar so it knows when it should stay put.


Is this what you had in mind or did you want something more fancy?

Have you seen TOBI the tool box carying bot? http://letsmakerobots.com/node/7025

I was thinking along the same lines as Bird, but since you mentioned force/pressure sensors, consider something like: http://www.pololu.com/catalog/product/1697

Run one of these along the outside of the handle and you'll have a built in means of determining the speed. More force detected means speed up because the user is pushing. No force at all means slow to a stop. Put one on the inside if you want a "pull" (reverse) version of the same.  You'd probably want a log function to grade the speed up to its max (if it turned out the FSRS responded linearly.) An ultrasonic sensor on the front could be used to keep old codgers from using it as a ramming weapon against their competitors.

Force/pressure sensors would work just fine. I was just shooting for low hanging fruit. :) And, no I don't know of any companies that build serious prototypes.

Thanks for this great idea and your good artwork! By the way, I'm French and will be keen to propose it as the 2012 master piece at Louvre Museum!

Do you think that force/pressure sensors can also do the job? For example from Tekscan?

Do you know companies who could built "serious prototypes"? I mean prototypes close to something to be produced in series.

Take a conductive tube, insert a slightly smaller tube partitioned into two zones (front and back WRT the cart), separate the two by a reasonably compressible foam or rubber, add an ultrasonic sensor to know when no one is pushing due to a lack of proximity. You might need to ... forget that mess of tubes.

Mount a switch front and back of the handle, add a pair of vertical plates that a bar ... picture = 1000 words, hopefully. :)

Yes, my artwork will never grace the Louvre. Hopefully though, it gets the point across. The two switches tell a microcontroller that someone is pushing or pulling. Add the ultrasonic to make sure some one is near, maybe instead, add capacitive touch to the bar instead of a ultrasonic for people sensing. And the rest is up to you and code.