# velocity continuously controllable **URL:** \ **Category:** Motion System Design\ **Created:** [January 27, 2014, 2:43pm UTC](https://forum.deltamotion.com/t/velocity-continuously-controllable/255 "2014-01-27T14:43:11Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![mars\_bruce\_lee](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/m/a587f6/32.png) [@mars\_bruce\_lee](https://forum.deltamotion.com/u/mars_bruce_lee)\ **Post date:** [January 27, 2014, 2:43pm UTC](https://forum.deltamotion.com/t/velocity-continuously-controllable/255/1 "2014-01-27T14:43:11Z")
Project requirements: velocity: 2 ~ 500mm / s continuously controllable。 Some people think that it’s difficult to Achieved ,because high cylinder and slow cylinder material is different 。 Is it right? ---
**Author:** ![Jacob\_Paso](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/j/439d5e/32.png) [@Jacob\_Paso](https://forum.deltamotion.com/u/Jacob_Paso)\ **Post date:** [January 27, 2014, 6:42pm UTC](https://forum.deltamotion.com/t/velocity-continuously-controllable/255/2 "2014-01-27T18:42:47Z")
We regularly achieve both speeds on our hydraulic systems here. For example, we have a cylinder with a 2 inch ( 50.8 mm) bore, and 24 inch ( 609 mm) stroke, and it is easy to achieve very slow speeds, such as 2 mm/sec, high speeds, such as 50 in/sec (approximately 1.3 inch/sec). A well-designed hydraulic system should be able to do that easily. This means that the valve should be located as close as possible to the cylinder, preferably on the cylinder. A servo-quality valve should be used, and the position feedback should be of high resolution. The cylinder should be designed with good-quality seals. If the system is not well-designed, then at low speeds, the static friction of the cylinder can cause a slip-stick action that creates jerky motion. An important question when requiring a very slow speed is how long the measurement interval is. For example, do you need 2 mm/s over 1 s, 0.1 s, 1 ms, or 1 μs? This can drastically change to system requirements, since achieving a slow speed measured accurately over a time of 0.1 second is much easier than over 1 μs. Usually, our customers just need the velocity to be “reasonably smooth”, and any well-designed hydraulic system can do that. ---
**Author:** ![mars\_bruce\_lee](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/m/a587f6/32.png) [@mars\_bruce\_lee](https://forum.deltamotion.com/u/mars_bruce_lee)\ **Post date:** [February 11, 2014, 3:18am UTC](https://forum.deltamotion.com/t/velocity-continuously-controllable/255/3 "2014-02-11T03:18:52Z")
> [@Jacob Paso](#): > > We regularly achieve both speeds on our hydraulic systems here. For example, we have a cylinder with a 2 inch ( 50.8 mm) bore, and 24 inch ( 609 mm) stroke, and it is easy to achieve very slow speeds, such as 2 mm/sec, high speeds, such as 50 in/sec (approximately 1.3 inch/sec). > > A well-designed hydraulic system should be able to do that easily. This means that the valve should be located as close as possible to the cylinder, preferably on the cylinder. A servo-quality valve should be used, and the position feedback should be of high resolution. The cylinder should be designed with good-quality seals. If the system is not well-designed, then at low speeds, the static friction of the cylinder can cause a slip-stick action that creates jerky motion. > > An important question when requiring a very slow speed is how long the measurement interval is. For example, do you need 2 mm/s over 1 s, 0.1 s, 1 ms, or 1 μs? This can drastically change to system requirements, since achieving a slow speed measured accurately over a time of 0.1 second is much easier than over 1 μs. Usually, our customers just need the velocity to be “reasonably smooth”, and any well-designed hydraulic system can do that. thank you for your reply。 e.g. the min speed= 2mm/s max speed=500mm/s 500mm/s Corresponding voltage 10v,that means 2mm/s Corresponding voltage=(2/500)\*10=0.04v qestion 1: I want to know Whether the resolution of the analog output can meet the requirements？ the resolution of the ssi module analog output=10/2048=0.0049? qestion 2:about measurement interval Project requirements : speed: 2mm/s Amplitude ：1.8mm frequency: 10hz sine what should i pay attention ？？ ![1.JPG](https://forum.deltamotion.com/uploads/default/original/1X/96850cb5ccc9d82c89deadaf29176b2753c5c434.jpeg) ---
**Author:** ![Jacob\_Paso](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/j/439d5e/32.png) [@Jacob\_Paso](https://forum.deltamotion.com/u/Jacob_Paso)\ **Post date:** [February 14, 2014, 5:22pm UTC](https://forum.deltamotion.com/t/velocity-continuously-controllable/255/4 "2014-02-14T17:22:59Z")
Answer 1: Yes, the analog output can meet the requirements for the slow velocity, because in closed-loop control, the analog output is continuously changing at a frequency of 1 kHz. The system response is much less than 1 kHz, so the analog output is basically averaged and results in a very well-controlled velocity. Answer 2: I think the standard settings in the RMC will work just fine. These are very typical requirements that the RMC can easily meet. Just follow proper system design, such as high-resolution feedback, a servo-quality linear valve with a zero-lapped spool, the valve mounted on the cylinder or as close to the cylinder as possible.