PMW’s high torque in-wheel motors have a number of advantages in the agricultural machinery sector, such as less damage to crop rows, less soil compaction (compared with heavy industrial motors) and being highly compact, they leave more available space on agricultural robots.
However, direct drive motors for agricultural applications are not recommended when a high level of torque at very low speeds is required. This is because a direct drive motor is inefficient at low speeds and high torque, and consumes a very high current. Battery life would therefore be short, and the assembly very heavy.
PMW instead recommends using a low ratio gearbox, since a shaft motor + gearbox combination has the following advantages over a direct drive wheel motor:
- A gearbox is more rugged when travelling across holes and rocks.
- The motor to gearbox to wheel assembly is easier to seal against dust and water.
- A gear-motor combination is likely to be more efficient for longer battery life.
- A gear-motor combination is likely to be less expensive than a wheel motor of this torque and speed.
Application: a milk analyser
The leading manufacturer of milk analysers, as used in dairies and on farms worldwide, uses GPM12 brushed pancake motors from PMW.
The motor is used to spin the milk samples at high speeds to separate the cells prior to analysis.
The GPM12 was chosen because of its short axial length and fast, smooth acceleration and deceleration.