A brushless drivetrain for a heavy mobile robot
Above ten kilograms, brushed gear motors stop being practical. This guide covers what changes when you move to brushless, including the parts that have no equivalent on a small robot.
AdvancedTarget budget €900.00From €83.65 with the cheapest option at every step
1.Motors× 2
A brushless motor with a low KV rating turns slowly and pulls hard, which is what a drivetrain wants. High KV motors are built for propellers and need a reduction stage to be usable on wheels. Hub motors integrate the reduction and the bearing and remove most of the mechanical design work.
Assembly
- Compute the wheel speed you need, then divide by your wheel circumference to get revolutions per minute.
- Divide that by your pack voltage to get the KV rating that suits, and pick below it rather than above.
- Check the shaft diameter and the mounting pattern against your wheel hubs before ordering.
2.Controllers with position feedback× 2
A hobby ESC has no idea where the rotor is at low speed and stutters on start. A field-oriented controller with an encoder or a hall sensor input gives smooth torque from zero, which a robot needs and an aeroplane does not. Regenerative braking is the second reason to prefer them on a heavy robot.
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Contrôleur Moteur Brushless 400W Accessoires Brushless Motor Controller
€28.70
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Contrôleur de Moteur Brushless 6,5 à 36V, 1A Tiny V2
€31.93Rated 4.5 out of 5, 4 reviews
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3.Emergency stop and contactor
A robot of this mass needs a way to cut motor power that does not go through software. A latching mushroom switch driving a contactor on the pack side is the usual arrangement. The logic stays powered so the robot can report why it stopped.
Assembly
- Rate the contactor above the stall current of every motor together, not above their nominal draw.
- Wire the mushroom switch as normally closed, so a broken wire stops the robot instead of disabling the stop.
- Place the switch where it can be reached from outside the robot's reach envelope.
4.Wiring and connectors
Currents in this class turn undersized wire into a heater and a marginal connector into a failure point. Size the conductors on the continuous current with a temperature margin, and use connectors rated for the peak rather than the average.
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