Linear Actuators

[Hunterfox]

Hi there

Can anyone tell me what is a acceptable duty cycle for a electric linear actuator in a sim?

[motiondave]

if you mean speed per second, the going rate is about 200mm per second or quicker for race.
Obviously less for flight.

[sirnoname]

agree, 150 is the lowest end.
The acceleration of your body can be another point, I did not see any comments about this value and what is common for it.

[motiondave]

acceleration of the body? Haven't heard that before.
I guess you are suggesting that if an actuator moves at 200m per second with 100mm throw, depending on where its mounted, the body moves a lot more.

[John]

I think the OP has been answered but duty cycle relates to how long you can use the equipment before it cuts out or causes damage and is usually stated as a percentage of time. For sim's the duty cycle should be 100%.

Regarding the quoted milimeters per second (mm/sec) how does XSIM real feel software deal with this ? We have static loads on the actuator during at rest and constant speed, and dynamic loads during acceleration and change of direction. Is there a better way of stating this movement, whether steady or changing, in relation to the way the software creates the movement?

The body senses pressure regarding acceleration and turning (lean) but the head must contribute to the "feel" and so, is the speed or rather the acceleration of the head a better measure for the purposes of determining the required specification of movement. That movement would then need to be converted into an appropriate actuator depending on the type and location on the sim.

Since our requirement is repeated changes in direction perhaps the minimum actuator movement could be specified as from closed to extended of say 200mm in one sec, for example, accelerating all the way. ( And how many G's is that on the head? There is an AP for smart phones on U tube that shows G's pulled as a dot which moves from a zero centre point, if any one would like to measure the G pull on their sim)

[Hunterfox]

Thanks John for that info, I see your average actuator's duty cycle is about 25%, of which then it wont even come close for simulator applictions.

[tronicgr]

What's duty cycle and how is it calculated?
Duty cycle, measured in inches per hour, is the total distance an actuator may travel (extension and retraction) in an hour with equally spaced intervals between each cycle. Duty cycle may also be expressed as a percentage, which is simply the ratio of on time to total time (on and off time). AC actuators operate between no load and rated load with very little change in duty cycle. In DC models, duty cycle is approximately inversely proportional to load (percent of rated capacity).

Calculating Duty Cycle
The duty cycle indicates both how often an actuator will operate and how much time there is between operations. Because the power lost to inefficiency dissipates as heat, the actuator component with the lowest allowable temperature (usually the motor) establishes the duty-cycle limit for the complete actuator. (Of course, there are some heat losses from friction in a gearbox and via ball-screw and Acme-screw drive systems.)
To demonstrate how the duty cycle is calculated, assume an actuator runs for 10 seconds cumulative, up and down, and then doesn't run for another 40 seconds. The duty cycle is 10/(40+10), or 20%. If duty cycle is increased, either load or speed must be reduced. Conversely, if either load or speed decreases, duty cycle can increase.
The duty cycle is relatively easy to determine if an actuator is used on a machine or production device. In other, less predictable applications or those where the actuator will be used infrequently, it's advisable to estimate the worst-case scenario in order to assign a meaningful duty-cycle calculation.
Note: Operating on the edge of the manufacturer's power curves might incur the risk of an actuator running hot. However, in some applications where the duty cycle is 10% or less, the actuator can run to the limit of its power curves.