Step 1: Use Any MCU Controller and DC Motor Driver to Control the Robot
Because L293D warms pretty much an aluminium heat sink is mounted on it.
The 6 volts accumulator is used as a power supply.
L7805 5 volts regulator is to supply valid level power to the controller circuit.
This controller could have less contacts - this board was made to be used in other prototyping.
This ATMega MCU was programmed by BascomBasic.
Step 2: Step-up DC Power Converter
Step 3: Reverse Side of the Controller Board
Resistor are to limit current between bumper contacts and MCU input pins.
The circuit is sort of "reverse engineered" by a soldered board (as I lost the original schema).
Step 4: Plastic Jar As a Cover Case
Step 5: Assembling
For such work it's easy to use steel belt for wall mounting works.
Motors, gears and wheels are from toy car.
Computer cooler turbine is mounted on the cardboard box.
Step 6: Dustbin
Air with dust comes into the aperture in the bottom of the dustbin box and goes out through the fabric which collects dust.
A tiny wheel for furniture is mounted as a third supporting point.
Step 7: Bumpers
Step 8: The Robot in Action
The attached program is written in Bascom Basic. It could be even shorter but this one contains extra code which avoid the robot be stack in corners for a room. The program was found among other versions, so I'm not sure it was latest one.