# To programatically control acceleration of a robot arm? **URL:** \ **Category:** General Guidance\ **Created:** [October 30, 2016, 9:32am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818 "2016-10-30T09:32:02Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![csanyi\_pal](https://avatars.discourse-cdn.com/v4/letter/c/ed8c4c/32.png) [@csanyi\_pal](https://forum.arduino.cc/u/csanyi_pal)\ **Post date:** [October 30, 2016, 9:32am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/1 "2016-10-30T09:32:02Z")
Hi, I am thinking about a project with one robot arm that should throw away a ping-pong balls in to two baskets. There should be two or three baskets in different distance from the arm. The balls should have different colors, say green and red only. The balls should get automatically rolls into the robot arm's palm. A sensor should detect the color of the actual ball in the robot arm palm. The arm should throw away the ball in to the correspondig basket number 1 or 2 that depends on the color of the ball. The essence of this project is the accelerations that get balls to fall in to a corresponding basket. 1. Can a servo been controlled to get different accelerations? 2. If option #1 is not possible, then mybe the servo should used just to pull a spring, and a relay should free the spring so the ball can be throwed away? Is this goal can be achieved with Arduino UNO and a corresponding robot arm? Best, Pali ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [October 30, 2016, 10:48am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/2 "2016-10-30T10:48:09Z")
I'm not sure that acceleration is the correct word. The distance an object "flies" after being thrown depends on the release velocity and the vertical angle it is moving at at the moment of release. I don't know if a servo would be suitable. Their speed is determined by their internal system. It is possible to give the appearance of slowing them down by getting the Arduino to move them in short steps - see the Servo Sweep example. But each small movement will be close to the full servo speed which may not be suitable for your project. I suppose it may be possible to adjust the range entirely by using a constant release speed and adjusting the trajectory. Lots of opportunity for some interesting experiments. ...R ---
**Author:** ![csanyi\_pal](https://avatars.discourse-cdn.com/v4/letter/c/ed8c4c/32.png) [@csanyi\_pal](https://forum.arduino.cc/u/csanyi_pal)\ **Post date:** [October 30, 2016, 11:28am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/3 "2016-10-30T11:28:38Z")
Hi Robin2, thank you very much for explanation of the problem. Then I should use one servo to adjust the trajectory angle, and another servo to throw away the ball. Right? ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [October 30, 2016, 11:37am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/4 "2016-10-30T11:37:22Z")
> [@](#): > > Then I should use one servo to adjust the trajectory angle, and another servo to throw away the ball. I can't answer that as you have not provided any diagram of the mechanical arrangement of your machine and I am very conscious that servo arms move in circles, not straight lines. It just occurred to me that you could use a servo to compress a firing spring and the amount of compression could determine the force on (and velocity of) the projectile. ...R ---
**Author:** ![DrDiettrich](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/drdiettrich/32/219048_2.png) [@DrDiettrich](https://forum.arduino.cc/u/DrDiettrich)\ **Post date:** [October 30, 2016, 10:30pm UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/5 "2016-10-30T22:30:45Z")
Also a solenoid may be usable for pushing the ball. ---
**Author:** ![csanyi\_pal](https://avatars.discourse-cdn.com/v4/letter/c/ed8c4c/32.png) [@csanyi\_pal](https://forum.arduino.cc/u/csanyi_pal)\ **Post date:** [November 11, 2016, 5:20am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/6 "2016-11-11T05:20:19Z")
> DrDiettrich: > Also a solenoid may be usable for pushing the ball. How can a solenoid push the ping-pong ball? ---
**Author:** ![TomGeorge](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tomgeorge/32/215261_2.png) [@TomGeorge](https://forum.arduino.cc/u/TomGeorge)\ **Post date:** [November 11, 2016, 6:19am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/7 "2016-11-11T06:19:50Z")
> DrDiettrich: > Also a solenoid may be usable for pushing the ball. I think the OPs aim is to THROW, rather than FIRE like a gun, the ping pong ball. So the servo arm swings and stops to send the ball on a hopefully predicted trajectory. The coding would have to set the stop position and the velocity at that position to send the ball on its way. The need is to see if a servo arm can attain the velocity, try different lengths of throwing arm. Tom..... 🙂 ---
**Author:** ![TomGeorge](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tomgeorge/32/215261_2.png) [@TomGeorge](https://forum.arduino.cc/u/TomGeorge)\ **Post date:** [November 11, 2016, 6:34am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/8 "2016-11-11T06:34:20Z")
Hi, If you google.. arduino arm throwing [www.instructables.com/id/Arduino-Controlled-Catapult/](http://www.instructables.com/id/Arduino-Controlled-Catapult/) > **[Robotic Ping-Pong Ball Launcher](https://www.youmagine.com/designs/robotic-ping-pong-ball-launcher)** > > This is something that I made for a Cub Scout "Invention Convention" pack meeting. At one station, we taught the kids to use TinkerCAD (www.tinkercad.com), which is a very easy to learn, useful, free, online CAD package, which I used to design the... they are fairly complicated but even look up catapult. Tom.... 🙂 ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [November 11, 2016, 9:25am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/9 "2016-11-11T09:25:57Z")
> TomGeorge: > I think the OPs aim is to THROW, rather than FIRE like a gun, the ping pong ball. The ping pong ball won't know the difference. All it cares about is the direction and speed at which it is released. ...R ---
**Author:** ![TomGeorge](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tomgeorge/32/215261_2.png) [@TomGeorge](https://forum.arduino.cc/u/TomGeorge)\ **Post date:** [November 11, 2016, 10:01am UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/10 "2016-11-11T10:01:51Z")
> Robin2: > The ping pong ball won't know the difference. All it cares about is the direction and speed at which it is released. > > ...R There is something more elegant about a catapult/trebuchet than a gun. Tom... 🙂 Not sure if its the OPs education project. ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [November 11, 2016, 1:33pm UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/11 "2016-11-11T13:33:26Z")
> TomGeorge: > There is something more elegant about a catapult/trebuchet than a gun. Perhaps - but both are intended to kill people. ...R ---
**Author:** ![TomGeorge](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tomgeorge/32/215261_2.png) [@TomGeorge](https://forum.arduino.cc/u/TomGeorge)\ **Post date:** [November 11, 2016, 5:20pm UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/12 "2016-11-11T17:20:32Z")
Hi, This project looks like an example in ballistics. Baseball pitchers, cricket bowlers, lacrosse players, tennis players, darts players and golfers all use ballistic theory.... All from a swinging arm... 🙂 ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [November 11, 2016, 5:27pm UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/13 "2016-11-11T17:27:28Z")
> TomGeorge: > Baseball pitchers, cricket bowlers, lacrosse players, tennis players, darts players and golfers all use ballistic theory.... I had assumed that is where the OP is coming from. I don't assist with weapons projects. ...R ---
**Author:** ![csanyi\_pal](https://avatars.discourse-cdn.com/v4/letter/c/ed8c4c/32.png) [@csanyi\_pal](https://forum.arduino.cc/u/csanyi_pal)\ **Post date:** [November 11, 2016, 8:07pm UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/14 "2016-11-11T20:07:16Z")
> Robin2: > I had assumed that is where the OP is coming from. I don't assist with weapons projects. > > ...R Throwing a ping-pong ball is not a weapon project. ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [November 11, 2016, 10:17pm UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/15 "2016-11-11T22:17:57Z")
> [@](#): > > Throwing a ping-pong ball is not a weapon project. That's why I am still here. ...R ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [May 5, 2021, 6:00pm UTC](https://forum.arduino.cc/t/to-programatically-control-acceleration-of-a-robot-arm/415818/16 "2021-05-05T18:00:49Z")