Progress Report

Its been to long since the last update testing is proceeding slowly localization is improving, rotation is still a problem. Increasing reliability has been one of the  goals  and improving the design to achieve this requires a 3D printer so i can make the custom gears and brackets. So i started making the printer that can double as a milling machine for milling parts and PCBs.
The printer uses draw runner as sliders they work rather well the NEMA 17 stepper motors may be a bit small but they will do for testing later they can be used in the base as steering motors

To Arms

No not a battle cry but what good is a robot with out arms if you noticed Robbie has a arm but with the AX12 servos and springs it can barely move and the shoulder lift servo will over heat quickly even with out the extensions. The price of larger servos is not an option. The torque required for a arm 90cm long to lift a 2 kilo object is over 1000 Kg/cm for the shoulder lift joint. After a bit of research i think i will use stepper motors at least i can start out using some of the old stepper motors and gears i have lying around. I plan to use the steppers for the first 4 joints in the arm at the moment just using motors from a old printer and a arduino to interface with ROS

Navigation Testing

A video of Robbie driving around under joystick control to test localisation
it works fine but after a while he gets lost

Improvment

Over the last couple of weeks I have been hard at work refining the control, localisation and general drive functions. While we are not at the stage of autonomous navigation short runs will work. The big fix is still odometery and how the base responds to navigation commands from ROS, The steering is always "fishing" for direction causing the robot to dart from side to side

Control Update

Finally got around to adding a reverse and fixed a fixing a major problem with the steering going haywire every now and then. This was caused by reverse actually trying to turn the wheels to 180 degrees (limit is 150). After this   we can now drive on joystick control without the wheels going out of calibration.we need to add a larger dead band around zero's

Adding IMU

Today we added a CHR UM6-LT IMU to the omni bot communications is through a sparkfun   FTDI board
the first problem we encountered was the RX and TX line need to be reversed. The other problem was
quanterions need to be enabled which can only be done in windows.
After downloading the ROS package  imu_um6 (searching ROS under sensors not IMU) and
launching we were publishing data from the IMU. Next step is to add a covariance matrix and run robot pose  EKF

Omni actions

Just a quick note the actions move_to_fish_tank and go_home work in directory robbie