February 1, 2014

Pneumatics projects

 

 

WALL CLIMBER


Wall Climber Robot that was developed at Robotics Interset Group (RIG), NIT Calicut. This Robot uses suction mechanism to climb on any surface.

 

 

WALL CLIMBER ROBOT

 

 

Working :

The robot is initially placed on an arbitrary location on a perpendicular wall. Once the power supply is given it starts to climb vertically upwards until the ultrasonic sensor senses the end of the wall edge. The upward motion is achieved by the following mechanism:-

At first the two lower suction cups grip the wall. To create vacuum pads are being used, which use compressed air. the piston moves forward with the help of a 5/2 valve. The forward suction cups grip the wall and the lower ones loose contact with the wall. Now the piston is made to contract. Therefore the given motion results in the forward motion of robot.

 

The robot then moves in the horizontal direction with the help of servo motors and suction cups. The arms projecting out of the robot rotates with the help of the servo, the suction cup attached to the arm grips the wall. now the other suction cups on the body of the robot loose contact with wall. Then the servo rotates back to the initial position . In this process the full robot swings on the arm. Once it is hanging just below the arm, the suction cups on the robot body grip the wall. This gives robot a side ways diagonal motion. It moves this way until it reaches the side edge which is sensed by the ultra sonic sensors.

 

To move to the adjacent perpendicular wall, the robot’s second layer flips by 90 degrees with help of a servo motor. Then the suction cups on the second layer grip the wall and the suction cups on the first layer leave contact with wall. Then the servo rotates in opposite sense to come back to its initial position . Therefore the first layer now flips onto the second layer thus transferring itself into a perpendicular wall.

Arduino development board is being used in this project. Mosfet motor driver is being use to control the pneumatic direction control valves, vacuum generators and servo motors on the robot.

 

Difficulties faced:

  • Due to the rotation of the piston, the suction cup position was prone to changes. The alignment of the suction cups in one plane so that they grip the wall properly. This was solved by placing two suction cups instead of one.
  • the side ward motion was difficult to achieve since the complete weight of the robot had to come on a single suction cup. therefore this was solved by putting a suction cup of greater diameter since it can take more weight.

Features:

  • Miniature straight motion robot.
  • Leaves no tracks on the wall after navigation.

Drawbacks:

  • Long Pneumatic wiring
  • Proximity to the Air Compressor
  • Compressed air leakage in the form of exhaust from

Applications :

  • Wall cleaning.
  • Aquatic tank cleaner.
  • To navigate on large tunnels or deep underground mining holes with rectangular cross sections.

OTHER PNEUMATICS PROJECTS

 

PNEUMATIC 2D PLOTTER

 

 

Working :

Using Image Processing techniques an image which is properly edge filtered is plotted by plotting each point of it. The whole information was fed into an sd-card in which the processed image file is stored.

Several Observations were taken and analyzed using Regression Analysis to make the plotter pen go to a particular xy co-ordinate. 5/3 valves were calibrated taking 50 observation along each co-ordinate axis. Regression analysis was used to obtain an optimum line plotted for time delay against distance to be reached. This increased the precision of Switching time of 5/3 valves. An error of less than .6 cm was achieved.

The Plotter pen was moved up and down using a Servo motor and a Rack and Pinion. The rack was attached to the pen and pinion was rotated to a specific back and forth angle using the servo. Initially this was done using an air Cylinder of 5cm stroke ,but later changed as the piston’s Inherent rotary property was drastically reducing accuracy of plotting.

Challenges faced :

As this project was aimed at developing a low cost precision plotter, improving accuracy of 5/3 valves was a challenging task. Achieving repeatability was a robust task. Proper point placing was not possible in the earlier stage, but was achieved later using a rack and pinion. Inaccuracy in plotting points in the half way of the piston stroke has to be solved.

Future aspects :

Presently only point plotting is achieved. This can be extended to horizontal and vertical line plotting. Curve tracing can be achieved using stepper motors or position feedback cylinders.

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