Drivebase - change speed during driving

[zoligyenge]

Hello. I was wondering whether it is possible to change the drive speed while the drivebase is running, i.e. without stopping.

The use case is: coverig large distances at high speed but slow down towards the end to be able to stop abruptly, for example when sensign an obsactle.

I tried with a multitask, but configuring the driving speed does not seem to have any effect.

[laurensvalk]

You could wait for an obstacle like this example: https://pybricks.com/learn/sensors/responding-sensor-values/#using-the-wait-until-block. And then instead of stopping as done here, this is where you could give a new drive command with a lower speed if you like.

You can also combine movements without stopping, if that is what you mean: https://pybricks.com/learn/making-programs/basic-robot-navigation/#combine-movements-without-stopping

So you could make the first command drive at some speed, and tell it not to stop at the end. Then drive another command at a new speed. It will change speed smoothly without stopping.

[zoligyenge]

Thanks. but not quite what I was lookign for. But apparently it is not possible to the change speed of a running drive command.

The idea is to only reduce the speed after a while not to stop and issue a new command. But I guess driving fast for (FastDistance-slowDistance), continue and then drive slowly for (slow distance) would be a workaround.

[laurensvalk]

The idea is to only reduce the speed after a while not to stop and issue a new command.

This is exactly what the second approach does. It doesn't stop but reduces the speed.

[zoligyenge]

Thanks again.

Indeed, however, for this aprpoach, if my "slow-down" is not distance based (but for example condition-based), then in order to be able to issue the second drive command so that the total distance is unchanged, I need to calculate how much I travelled until the "slow-down" executed to be able to issue the new slow drive command with the precise "leftover" distance.

For example: I know that somewhere around 1000mms ahead there is an object I want to pick up.

I want to drive as fast as possible, but when my distance sensor starts to detect something, I want to be able to slow down and be able to stop at any moment. At the same time I don't want to stop to early, only at an exact distance. ALso, if my distance sensor picked up soemthing on error, I want to stop exactly at 1000mms.

[BertLindeman]

Maybe a simpler example?

[EDIT] Replace the waits by the conditions you need.