Wheel Kit

SailerMan

Has anyone been using the Parallax Wheel Kit with encoders, I have been going back and forth deciding if I should buy these.

One thing that concerns me is the applicable commands that can be sent to the encoder boards. If you say for instance send a command to move forward you tell it the number of steps to move.. but what if you are looking to make a free roaming robot.. that uses sensor data to determine your course.

For some reason I can't get around thinking if I set the wheels to move in a direction say 500 steps and approach say a wall... how can I veer away from the wall and continue on with the original 500 step movement.

Am I making any sense?

For those of you using these wheels do you think they were a good investment?

Thanks for any help,
Eric

Brian Carpenter

make a loop that only moves 1 step. Looks around and then steps again.

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It's Only A Stupid Question If You Have Not Googled It First!!

Ken Gracey

Eric,

You can control the MMWK through the encoder board, or directly from the HB-25s. You could provide a free-roaming sensor-based proportional control with or without the encoder hardware. I've used them on my robot without the encoders, actually, under direct control from the microcontroller. I found it a bit simpler than through the encoders.

- Ken

SailerMan

I'm assuming that I can still keep track of encoder counts for some rudimentary dead reconning... or If I need to turn 90 degrees I can still us the encoder board for specific commands.

Is it a choice I have to make between with or without the encoder board?

Thanks,
Eric

Dgswaner

Eric, I have dealt with exactly what your talking about. I used Norris56's cod for the propeller(momo control). His code has 2 turn types. turning while standing still and turning (veering) while moving. turning is your basic turn, wheel A goes forward wheel B goes backward. the speed control function of the encoders make veering quite easily. you simply slow down one motor for X amount of time to turn the desired amount. set it back to the desired speed and your going straight again.

What I did was start in a loop that sends 100 +/- "counts" forward. you then check to see if anything is in the way. if anything is determined to be in the way you then send a stop, turn etc. If your at step 50 going forward. and you need to turn you send a stop command (sets the counts to 0), then a turn command and then go command. to Veer you slow one side. and continue forward after the turn (counts are not reset)

although I haven't done it, I've believe it possible to have a couple Propeller cogs keeping track of dead reconning coordinates. and at the same time have the locomotion control in the free roaming fashion.

I started bot building with servos, then tried relays, HB25's and finally the encoders with the hb25's. and once you use them you'll never want to go back. you can achieve much more fluid and natural movement. no more herky jerk starting and stopping. They are worth every penny!

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DGSwaner

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"When in doubt, use C4" - Jamie Hyneman, Myth Buster

SailerMan

So are there spare parts available for the Wheel Kit?

Manetheren

Why not just leave the number in the count loop and when you check just come back to that point in the loop. Once a full loop is completed then you reset the count back to 0.

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Tia'Shar Manetheren

Searider

SailorMan,

I have driver for the Wheel Kit using the Parallax Possition Controller, that lets you give inputs in the form of Speed and direction (joystick). The driver manages the rest. The main issue that I had to compromise on was that you can not cleanly slow down unless it is to stop. This is a result of a design choice by Parallax to not ramp speeds when decreasing, only increasing. If you try the driver, let me know what you think.

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Searider

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