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How to maintain motion commands (440 Omni)

Posted: Wed Aug 14, 2013 4:30 pm
by trautman
Hi,

We are interfacing the RMP with our navigation program instead of the joystick. Is there a way to specify how long to maintain a motion command that is sent to the RMP, or instruct the RMP to maintain the motion command until a new command is received? So for example, if we want the RMP to go in a straight line for 30m, currently our navigation program has to keep sending the same motion command at a certain frequency, so the motion of the RMP is stop-and-go and jerky. We would like to have it behave more smoothly.

Thanks a lot!

Re: How to maintain motion commands (440 Omni)

Posted: Thu Aug 15, 2013 8:56 am
by sdnalloh
Take a look at the Controller Input Mapping section in the User Manual.

If you set the RMP to Acceleration-Based Input Mapping, you can send it acceleration commands instead of velocity commands. Using this method, you send the RMP acceleration commands until it reaches the desired velocity. Then you set the acceleration to zero and the RMP will continue to roll at the present velocity. To decelerate, you send a negative acceleration command.

Re: How to maintain motion commands (440 Omni)

Posted: Fri Aug 16, 2013 11:29 am
by phussey
Acceleration based mapping is purely for tele-operation and not ideal for the application.

The platform must be commanded at a minimum frequency in order to maintain smooth operation. You must update the commands at a minimum of 0.5Hz (twice per second) otherwise the command will be slewed to zero at the decel rate in between command resulting in jerky motion.

Re: How to maintain motion commands (440 Omni)

Posted: Fri Aug 16, 2013 6:22 pm
by trautman
We tried commanding at frequencies from 0.5hz to 50hz, but it's never smooth. So for the omni, we can't use acceleration based mapping, correct? The only motion command we can give is velocity (linear, angular, yaw rate)?

Re: How to maintain motion commands (440 Omni)

Posted: Fri Aug 16, 2013 6:26 pm
by trautman
The problem I think is the vehicle automatically decelerates during the execution of each velocity command, but what we would like is have it maintain that velocity for a duration until a new velocity command comes in. Is there a way to achieve that? Thanks a lot!

Re: How to maintain motion commands (440 Omni)

Posted: Tue Aug 20, 2013 3:45 pm
by phussey
I have run the testing with the current release (04-08-13) and the commands persist for 0.5 seconds before being slewed to zero. I tested from 0.5Hz to 100Hz with same results.

Have you verified the timing of your application and that the communication interface is not dropping messages? If I remember correctly you are using ethernet and possibly wireless. The protocol is UDP so there is no guarantee that the message is delivered unless your application is checking for responses to the command.

Without custom software development there is no way for a command to persist more than 0.5 seconds, primarily for safety reasons.