Squirrels have fuzzy tails.

0 Members and 2 Guests are viewing this topic.

Did you try using the RMF calculator?http://www.societyofrobots.com/calculator.shtml

acceleration to max velocity = 1.3m/s^2[...] but this results in a large torque

The torque I have calculated doesn't take into effect the acceleration to the max velocity. The maximum velocity is so small that the acceleration to that point is barely a transient in steady state.The torque I've calculated is based strictly on the weight of the vehicle. I just wanted someone to verify it for me.

The resultant torque was calculated from the result of the acceleration due to gravity.All I want to to know is how everyone calculates the torque of a load before picking out a motor.

QuoteThe resultant torque was calculated from the result of the acceleration due to gravity.All I want to to know is how everyone calculates the torque of a load before picking out a motor.The accelerate on a level surface gravity doesn't really come into the calculation. Only the Mass of the Bot.The forward force required is: F = ma (mass of bot * desired acceleration) = 2kg * 1.3m/s/s = 2.6 NewtonThe find the required torque on the wheel's axial use: Torque = wheel radius (moment arm) * Force = 0.0381m * 2.6N =0.099Nm = 0.010kilogram meter = 14 ounce inchIf the Bot needs to accelerate up a ramp than the required torque increases by mg * sin(ang) so the total F = ma + mg*sin(ang) where:g is the acceleration of gravity (9.8m/s/s on Earth's surface)m is the robot mass (kilogram)ang is the angle of the inclineSo for a 7.65° incline, a 2kg bot, 0.0381 radius wheels, acceleration of 1.3m/s/s the Force is:F = 2*1.3 + 2*9.8*sin(7.65°) = 2.6+2.61 = 5.21NTorque = 0.0381*5.21 = 0.20 Nm = 0.020 kilogram meter = 28 ounce inchThen to account for losses divid by 75% (0.75) so Torque = 37 ounce inchNote: I use an online conversion app for the different torque units here:http://www.onlineconversion.com/torque.htm

When the acceleration is zero (aka the velocity is zero),

If when the wheel is moving at a constant rate, and the torque then is zero as you say, then according motor principles the motor should stop spinning since torque is relative to speed.

If the velocity is zero and friction is zero the motor/wheels will turn at a constant speed determined by the voltage applied and the motor characteristics.

Quote from: waltr on November 25, 2010, 08:22:49 AMIf the velocity is zero and friction is zero the motor/wheels will turn at a constant speed determined by the voltage applied and the motor characteristics.I'm just pointing out a typo, it should be 'If the acceleration is zero and friction...'