I’m building my daughter an off-road wheelchair which at the moment is likely going to be 6-wheel-drive. Unfortunately, my knowledge of electronics is limited, but my motivation is strong. One of the things I haven’t been able to work out by myself is this:
Just to keep the math simple, let’s say a 100w motor will need to draw a constant of 10 amps to move a given object up a hill.
Question 1: How is power distributed if the number of motors increases? - If two motors produce 100w each, does that mean you have 200w power, or just 2 x 100w? I realise this is a confusing question and I’m not sure how best to put it. Is the pushing capability 200w or still just 100w?
Question 2: If one motor needs 10amps to push an object, does that mean that if I use two motors, they will then only need 5 amps each? I expect it’s not going to be as linear as this but just an overview would be great.
Thanks in advance, Glyn
For the same required power, adding motors means the power demand from each is lowered. Note however that a motor only consumes as much current as it needs in order to maintain a desired rpm. This means that although a motor might be rated for 100W, that does not mean it will always consume 100W (should consume less). For example if the motor is rated for 100W (12V nominal input voltage), but to move up the hill it only requires 5A (when using two motors), that means the total power draw for that motor is Power = Current * Voltage = 12V5A=60W. If you need two such motors to move up the hill, two motors would be 260W = 120W.
Assuming the motor is rated for 100W max, and (for example) 12V nominal, that means the max current draw for that motor would be 100W / 12V = 8.3A.
If you have two motors which can produce up to 100W each, you have 200W total available power, which is the same as 2x 100W.
Essentially yes. If you have a 2WD robot which has one drive motor on each side which can provide T (you insert a number) torque each to get up a hill, or 2* T total, then using four such motors, each motor would only need to provide 1/2* T. If you use three motors / wheels per side rather than just one per side, you’d need 1/3 T per motor. This does not factor in a bunch of “harder to calculate” factors such as efficiency, friction etc. which is why you should have a safety margin. If you need T, then choose a motor which can provide at least 25% to 50% more, so 1.25 T to 1.5 T.
