Add a known load to a DC motor

Hi everyone,

I have implemented PI control of speed of a PMDC motor under no load condition. I now intend to implement the same with a load added to it.
I want to compare the results with simulation as well. Is there any way of adding a known load to a DC motor. In my set up the dc motor is mounted on a metallic box.

Thanks,

An easy way to apply a variable load to any motor is connecting it to a stepper motor and powering up one (or several) of its coils with a controlled current. This controls the holding torque of the stepper, known from its datasheet, and thus provides an easy, cheap and readily available known load to any motor.

Theoretically, torque measurement is supposed to be done by attaching a known weight to a rope which is reeled up by the spinning shaft of the motor. The shaft is a known diameter. The resulting torque value is stated in foot-pounds.

This is a difficult measurement to take. It can only be done while the motor is spinning.

An alternative is to apply friction in some manner. (Example, cloth-covered clamp.) This tends to polish surfaces thus reducing friction, making this an unreliable test.

Another way is to create magnetic friction in the form of eddy currents. Attach a plate to the shaft and hold a magnet close to it while it spins. If not done carefully this could disrupt operation within the motor.

Another way to create a load is to make the motor spin a paddle, which is immersed in water to various depths.

Haven't heard of a DYNAMOMETER? A common mechanical loading device know since 19th century?

Couple it to another permanent magnet DC motor, which will now act as a generator, load it with resistors to increase load.
Frank