# velocity continuously controllable

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?

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.

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?