Hello readers! In last article Low cost window cleaning robot
we explained the first prototype we designed. We also explained the
short comings and failures of the design. But this was not the end! We
did further literature survey and came across the video of this wall climbing robot on YouTube.
It became our inspiration and we began to develop a robot using high speed brushless dc motor as seen in the video for creating vacuum between the surfaces.
As learned by previous experience the important parameter while designing the robot is the weight of body. It is important that the mass must lie at single point and by physics we commonly recall the concept as centre of gravity(COG).
The mass must be distributed in such manner that the entire system can be replaced by single point mass.
COG helps in reducing the recursive steps needed to calculate the force exerted by gravity on each component on the robot.
We designed the chassis on CAD and went for lazer cutting as shown in the article Sneak Peek.
The weight of the robot according to the new design had to be lower than or equal to 500 g. Our first design of the chassis was heavy and so we removed more acrylic in order to reduce the weight.
Finally when the chassis was designed, we placed our components as shown in the figure below.
As you can see we have placed the brushless dc motor
in the middle of the chassis and rest components like Arduino
development board, motor driver and ESC around the motor. The motor
driver we have used is to control the two gear bo motors for robot's
motion along the wall.
But unfortunately as we proceeded to test our prototype we faced some problem with our ESC(Electronic Speed Controller). We had bought 30A ESC whose rating was lesser than the maximum current rating of the brushless motor.
Please keep in note that use ESC whose current rating is greater or equal to 30%-40% of the maximum current rating of the motor.It ensures that your ESC will not get short if the motor drives high load.
Since we were using our motor to create vacuum to support the weight of the robot, it was driving large current from the battery.In every test runs the ESC would get really hot and soon the motor stopped working properly.We solved this problem by replacing the old ESC with larger current capacity of 40A.
Next we faced the problem with the BO motors.The motors had 1.5 kgf torque which is not enough to push the robot upwards.The motors with high torque are heavy and could not be placed on the robot. We did some research and found out about mini geared high torque motors.Due to budget constraint we could not implement it in our project.
But in the end, we were able to fulfill two out of four major objectives.
It became our inspiration and we began to develop a robot using high speed brushless dc motor as seen in the video for creating vacuum between the surfaces.
As learned by previous experience the important parameter while designing the robot is the weight of body. It is important that the mass must lie at single point and by physics we commonly recall the concept as centre of gravity(COG).
The mass must be distributed in such manner that the entire system can be replaced by single point mass.
COG helps in reducing the recursive steps needed to calculate the force exerted by gravity on each component on the robot.
We designed the chassis on CAD and went for lazer cutting as shown in the article Sneak Peek.
The weight of the robot according to the new design had to be lower than or equal to 500 g. Our first design of the chassis was heavy and so we removed more acrylic in order to reduce the weight.
Finally when the chassis was designed, we placed our components as shown in the figure below.
 |
| Figure 1 Top View |
 |
| Figure 2 Bottom View |
But unfortunately as we proceeded to test our prototype we faced some problem with our ESC(Electronic Speed Controller). We had bought 30A ESC whose rating was lesser than the maximum current rating of the brushless motor.
Please keep in note that use ESC whose current rating is greater or equal to 30%-40% of the maximum current rating of the motor.It ensures that your ESC will not get short if the motor drives high load.
Since we were using our motor to create vacuum to support the weight of the robot, it was driving large current from the battery.In every test runs the ESC would get really hot and soon the motor stopped working properly.We solved this problem by replacing the old ESC with larger current capacity of 40A.
Next we faced the problem with the BO motors.The motors had 1.5 kgf torque which is not enough to push the robot upwards.The motors with high torque are heavy and could not be placed on the robot. We did some research and found out about mini geared high torque motors.Due to budget constraint we could not implement it in our project.
But in the end, we were able to fulfill two out of four major objectives.
