Would it be possible to substitute GM17s for the GM9s that come with the Robot Rover? Solarbotics has begun selling a quadrature encoder that works with the GM17. The company name is Didel. Or perhaps you plan to sell these encoders?
Thanks very much for researching my question and for the picture. I had hoped to use the device for dead-reckoning, but came across an article that said encoders don’t work very well on tracked vehicles because of skidding. I still might buy one. They also have a motor controller on the card.
Would an IMU work for dead-reckoning and if so which one? I would think that I don’t need nine degrees of freedom.
BTW, I really like the DFRobotShop Rover. However, I would like to try something bigger for my next project like something based on the Lynxmotion Tri-Track Chassis Kit . I should probably finish my first robot first.
Would it be possible to substitute GM17s for the GM9s that come with the Robot Rover? Solarbotics has begun selling a quadrature encoder that works with the GM17. The company name is Didel. Or perhaps you plan to sell these encoders?
Hi Stonechild,
Good question. We had to test the GM17 physically and found the following:
The motor fits physically into the space very well, but the mounting holes do not align with the holes on the metal frame, and the shaft is ever so slightly smaller (so the drive sprocket is not a press fit). To keep the motor in place, you can use a bit of glue or double sided tape as well as the screw at the end of the shaft to hold the drive sprocket on. The GM17 becomes an excellent option for the rover since no modifications need to be done to either the motor or the frame. There also seems to be more than enough room for the encoder. We’ll look into carrying the encoders.
Encoders, even when used with wheels can always slip, thouh you are correct to assume that tracks inherently slip more than wheels. You can always add traction to the RobotShop Rover. An IMU has the issue of drift, but with proper coding (Kalman filter for example when used with encoders), it reduces the error significantly. You would only need a two axis accelerometer and single axis gyro. If budget allows, adding a compass module and GPS can eliminate the error (almost) entirely.
Hi zara678,
Welcome to the RobotShop Forum. The GM17 gear motors can be mounted to the RobotShop Rover frame, although the screw holes do not line up. You might need to use glue to keep it in place - there are screw holes which would be located outside the frame which may help a bit too. The GM cog does fit onto the shaft, but will definitely need to be secured with the little screw which is included in the hardware bag. We have not mounted the encoder option anthough it does look like it will fit. We should be able to offer the encoders as special order - please submit a ticket via the RobotShop Support Center and provide your complete telephone number and address (so we can create an account) and a list of the parts you would like to order, as well as RB-Sbo-00 51510 Didel GM17 Encoder(s). We cannot officially change the kit contents because of the mounting issue, although you can order the motors and encoders in addition to the RobotShop Rover.
Hope this helps,