Calculating Required Motor Torques

WIP for calculating the required torque, and modelling the 6-wheeled rocker bogie system.

VariableKnown (assumed) /UnknownSymbolValueUnitNotes
Gross WeightKnownWgTBDKg
Wheel DiametersKnownDTBDmAssumed all wheel diameters are the same
Rolling Resistance CoefficientKnowncTBDunitlessAssumed rubber tire on concrete
Time to accelerateKnowntaTBDsAssuming linear acceleration, how long do we want it to take to accelerate?
Maximum speedKnownVmaxTBDm/sAt the end of acceleration, how fast do we want our robot to be moving?
Slope AngleKnownθTBDdegrees (or radians)Angle of the slope that the robot is currently on

Calculating Force to Accelerate

Faccel = Wg * Vmax / ta

Calculating Force due to Slope

Fslope = Wg*sinθ

Calculating Force due to Rolling Resistance

Froll = cWg

Total Tractive Force Required

Ftract = Faccel + Fslope + Froll

Since we have 6 wheels. We device Ftract  by 6 to get the tractive force required per wheel, which is the required wheel torque.


21/08/27 Motor Torque Calculations

Loading ConditionNotesMinimum Torque, no SF (Nm)Safety factor for torqueMinimum Torque, 1.25 SF (Nm)Minimum Speed (RPM)

Hill climb

constant velocity

  • rolling friction assumed to be 0
  • expected loading duration 1 min
  • might require a surge beyond the calculated values < 10 s
8.671.412.187

flat ground

constant velocity

  • must be able to perform at this loading condition indefinitely
3.681.254.6223