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Motor Candidates

Motor Candidates

May 10, 2021

Ballpark torque required. Will require simulation of the loading on each wheel at different positions of the drivetrain to determine the exact torque we should spec for/validate our rough calculations. 

Parameters

  • Max rover weight: 50 kg

  • Max object weight for Extreme Retrieval and Delivery mission: 5 kg

    • Assuming we carry at max 2 rocks at a time

  • Assuming we operate under 48 V

  • Assuming the drivetrain will use 6 motors (each design we're considering is a 6wd and requires a motor per wheel)

  • Assuming a wheel diameter of 9", or 0.229 m

  • Ideally, with any variety of rocker-bogie design, the load is spread equally across the 6 wheels in any position

  • Setting a safety factor of 2

  • Assume a 10% efficiency loss per gearbox stage

Rough Calculations

1. Under our above assumptions, determine the weight acting upon a single wheel/motor

Estimate load per motor = [(50 kg + (2 rocks * 5 kg)) / 6 motors] * safety factor = ~10 kg per motor * 2 = ~20 kg per motor

2. Determine the force acting upon a single motor

Fmotor = 20 kg * 9.81 m/s2 = 196.20 N

Is this over-overestimate intended? This is the force required to lift the load vertically ie 90° slope incline

3. Determine the torque we need each motor and gearbox to produce in order to operate the drivetrain

Tdt = Fmotor x Rwheel = 196.20 N * 0.1145 m = ~22.465 Nm

Motor Vendors

Vendor

 

Vendor

 

https://odriverobotics.com/

 

https://www.electrocraft.com/

https://www.hansen-motor.com/

 

https://gemsmotor.com/

BLDC

BLDC Gear

https://www.maxon.net/en/

 

https://dingsmotionusa.com/

NEMA 34 BLDC Motor

https://www.dunkermotoren.com/en/

Brushed DC Motors

https://www.wonderfz.com/

Brushed DC Motors

Brushless DC Motors

http://vishanmotor.com/index.php

Slotless BLDC Motor EC Series

Slotless BLDC Motor ECH Series

https://www.3xmotion.com/

Brushless DC Motors

Brushless DC Geared Motors

https://technosoftmotion.com/en/home/

Intelligent Motors

Brushless Motor Suggestions

Motor Name

Price (USD)

Mass (g)

Max Voltage (V)

Body Length (mm)

Free Speed (RPM)

Stall Torque (Nm)

Stall Current (A)

Number of Pole-Pairs

Gearbox Suggestion

Motor Name

Price (USD)

Mass (g)

Max Voltage (V)

Body Length (mm)

Free Speed (RPM)

Stall Torque (Nm)

Stall Current (A)

Number of Pole-Pairs

Gearbox Suggestion

ODrive Dual Shaft Motor 150 Kv

$109

890

48

 

2880

3.86

70

7

 

Maxon EC 60 Flat

$147.84 (order of 1-4)

$129.93 (order of 5-19)

375

48

48

4020

4.87

43.2 

7

@ 15% less than than the nominal torque...

  • Motor torque = 490.45 mNm

    • Motor torque with a 30% efficiency loss = 343.315 mNm

    • Motor speed with efficiency loss = 3783 RPM

  • Current drawn = 4.340 A/motor

    • 26.042 A for the drivetrain

  • Required ratio = 66:1

66:1 Planetary Maxon Gearhead

  • 78.5mm in length

  • 770g

  • $432.63 (order of 1-4)

    • $371.63 (order of 5-19)

  • Max continuous torque of 30 Nm

Maxon EC Frameless 60

On request

333

48

37

3970

5.01

43.8

7

@ 15% less than than the nominal torque...

  • Motor torque = 271.15 mNm

    • Motor torque with a 30% efficiency loss = 189.805 mNm

    • Motor speed with efficiency loss = 3852 RPM

  • Current drawn = 2.38 A/motor

    • 14.27 A for the drivetrain

  • Required ratio = 119:1

Requires a custom housing to pair with a 83:1 or greater gearhead

Ex. 126:1 Planetary Maxon Gearhead

  • 78.5mm in length

  • 770g

  • $432.63 (order of 1-4)

    • $371.63(order of 5-19)

  • Max continuous torque of 30 Nm

Electrocraft RP23 BLDC Motor

 

 

160

 

4300

1.34

12.6

 

@ 15% less than than the nominal torque...

  • Motor torque = 442 mNm

    • Motor torque with a 30% efficiency loss = 309.40 mNm

    • Motor speed with efficiency loss = ~ RPM

  • Current drawn = 4.131 A/motor

    • 24.785 A for the drivetrain

  • Required ratio = 119:1

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