my goal is to use a simple, lightweight robot arm of approx. 20 cm length to throw a ping-pong ball. The arm should consist of one part and a gripper at the end. I want to throw the ball at an angle of 60°. During the planning, I have encountered some problems. To throw the ball at a maximum desired distance of ~9meters, I would need a angular rotation speed of the arm of about 45 rad/s. I researched a bit and found out that cheap servo motors come at approx. 0.15sec/60° which would be about 7 rad/s. So it seems like I need a special motor for this. Does anyone have recommendations which kind of motor would be suitable for this? Is it even feasible in this setup?
The robot arms main purpose is to be able to throw ping pong balls accurately, but I would like if it would be able to also pick up balls from the ground directly in front of it (the arm will be mounted on wheels). So the arm is intended to be only movable around one fixed axis. For holding and releasing I was thinking of using a claw design, although I do not know much about that as it is my first time using Arduino.
Using a robot arm and a claw, I would have tried to release it around the time the arm reaches an angle of 60 degrees. Probably a bit of adjustment would be necessary, but I think if I chose a suitable claw design the moment of release could function almost instantaneously.
Yes, that is what I am thinking right now. So I want to design a circular shaft where the ball sits on a platform. The platform is supported by and connected to a spring and a rod that goes throw a hole in the shaft. The rod will be pulled back by a motor and then released at the desired position. I am just not sure about the mechanism to release it. I was thinking about using another motor to drive a small stick inside a hole in the rod and connect them this way and for the release drive the small stick back.
Have a look how door latches work - so you pull back against a spring loaded catch , then pull catch back ( as in opening a door ) to fire .
If this is powerful btw - it could be construed as a weapon , especially if you kill someone
I think I am going in a similar way as your suggestion. I want to use a high-enough precision linear actuator in combination with a solenoid. The solenoid is attached to the actuator and will connect into the rod that is attached to the spring. Then, using the linear actuator, the rod will be pulled back such that the spring has the desired position. Then the solenoid is triggered, which releases the rod and with it the spring. Then, the process can be repeated by moving the linear actuator back to the initial position and then connecting again to the rod using the solenoid.
Remaining concerns:
-Precision of the linear actuator. I calculated roughly that I will need 0.05 mm accuracy / repeatability. I will first test with a lower cost actuator and if necessary upgrade to a new one.
-Other factors like friction and air resistance that are physically complicated and make it hard to keep a consistent precise throw.
I want the ball to be thrown with a precision of ~1cm. Calculating this using the formula of the potential energy of a spring which will be used to accelerate the ball, I found out that every approx. 0.05mm of added spring compression, the ball flies further by one cm. Of course I did a lot of approximations but generally this should be the precision I need. But is it really that hard to get this precision? I read that for precise linear actuators, the precision is often in the range of micrometers. So for a standard one with some kind of feedback loop I guess it would be possible.
