Robot Can Hold a Beer with a Robot Gripper – Mr Tidy


This robot is called Mr Tidy, built by Oddbot from China. Original post can be found here.

Mr Tidy has a robot arm which is also a robot gripper. He can pick up bottles and glasses after a party and put them in a tidy pile.The video shows him picking up his first can.

Mr._Tidy_holding_can

The Sensors

There are 4 IR obstacle detectors, one on each corner that will be angled downward to detect cliffs as well as walls. The IR sensors share a common analog input so switching the IR LEDs one at a time is required to read individual corners. These outputs also drive 4 normal LEDs for visible detection of operation  When the outputs change to inputs, 4 micro switches used for monitoring the gripper position can be read. These switches will only monitor the limits of travel for the arm / gripper.

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The Robot Gripper

The gripper is fitted with an RGB LED and an LDR to form a colour sensing “Amander LDR”. By reading the LDR when different colours are lit the robot can determine the colour of the object being picked up. This sensor will be angled downward to read the colour of the floor as well.
A conductive foam pressure sensor is used to determine how hard the robot is gripping an object.

Automatic Charging

Recharging will occur when the robot reaches a docking station. Electrical connections being made much like a dodgem car with charge whiskers at the top and a ground strap underneath. The docking station has an IR LED sending out an IR signal. This is detected by an IR receiver when the robot is facing the station. A voltage divider reduces the battery voltage to a safe level to be read by an analog input.

Motor Driver

The motors are driven by a L298N. Since this chip can only drive two motors, two DPDT relays are used to select between the drive motors and the arm / gripper motors. PWM is used to control the speed / power of the motors. A speaker has been added so that the robot can call for assistance if it runs into trouble.

Mr._Tidy_Schematic

 

 

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Robot and Controller Communication

Set up an Xbee interface for wireless communications between the robot and PC.

Xbee_attempt_1

Xbee_interface

Xbee_interface_Schematic

 

The Difficulties

Making Mr. Tidy autonomous is difficult. With no rangefinder sensors or servos he is basically a blind man with a white cane. So far the software has been improved with compensating for ambient IR very nicely by doing a calibration test on power-up. For this reason the robot must be in a clear area with no strong shadows when powering up.

Mr. Tidy is quite heavy with all that steel meccano and six AA rechargeable so turning on carpet was always a struggle for him even with tape on the wheels. Omni-wheels have been fitted on the front which has improved steering considerably.

Mr_Tidy_with_omni_wheels__small_

Oddbot is about to do a minor modification to the gripper Mr. Tidy could become Mr. Artist and hold a paint brush instead. He could identify different pots of paint from a distance using multiple IR beacons, each sending a different code to identify the colour. Up close the colour sensing Amanda LDR could be used as well. Just tape a large sheet of paper on the ground and use CTC’s folding fences for robots to keep the little bugger from painting the hallway 😀

 

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