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PWM (Pulse Width Modulation):
An efficient technique to
control current. A PWM-switched signal pulses on and off to achieve the current
flow required. PWM frequency can be low (100 to 400 Hz) or high (over 5000 Hz). High frequency produces a more constant ripple-free amperage output.
Dither (Current Ripple):
A rapid, small movement of the
valve spool around the desired position. Dither keeps the spool moving to avoid “stiction” and to help average-out hysteresis.
1. Applying dither to a valve reduces
actuator friction and reduces
hysteresis. A good rule of thumb is to use 70 -250 Hz dither frequency on all SP, ZL, and PV valves (flow and directional control valves), and 200-300 Hz dither frequency on TS Valves (proportional
pressure control valves). Otherwise, at lower frequencies the actuator will follow the dither signal and the valve
output will appear unstable.
You generally want to tune your dither frequency as low as possible, however, when you have system excitation, you will need to set the dither higher until the excitation goes away.
Higher frequencies have little effect on the valve, although at high frequencies, there is a slight increase in hysteresis. When tuning the dither for a poppet style valve, in the case of frequency matching, you would not want to use a dither frequency in the range of 15-50 Hz as it will cause instability and chattering of the poppet.
Nu är väl just Dither inte vad som spelar roll i första svängen. Jag skall ju inte reglera sliden. Utan "bara" ställa den i ett läge av eller på. Men de kunna välja på läget i lågt
flöde eller högt flöde.
Dither skall då påverka pulsbredden, så att sliden vibrerar. Då räcker det ju inte med att den påverkar PWM frekvensen.
Nybörjare på grävning. Satt 80 timmar i en Kubota kx151 innan jag köpte min första grävare september 2016.
