Motor Selection for Automotive Actuator

[rayclag]

I am working on developing a rotary actuator for an on-engine device. The actuator has to live in a harsh environment (temperatures of up to 150C and vibration level up to 25G's). What are the pro's and cons of the basic motor types Stepper, Brushless, and Brushed DC for operation in such an environment? Are there any other motors that should be considered as a basis for design?

 

[jbartos]

Suggestion: Any motor can be designed to fit the environment. Will you consider a custom made motor? The induction squirrel cage motors are often considered most rugged.

 

[UKpete]

rayclag, as you use the word actuator I presume you mean a limited-motion device. In addition to the basic motor types mentioned there are relay type rotary actuators eg Laws relay and toroidally wound actuators. It depends on your application - whether you simply want to swing between two end stops or whether (at the other extreme) you want fast-acting accurate continous angular control.

There are also other rotary devices that you may consider, eg the switched-reluctance motor (capable of giving fixed step motion), these are rugged and simple but not generally available off-the-shelf.

Stepper motors obviously have fixed steps and can be used open loop, so the drive requirements are simple and they have no accumulated position error, they have reasonable holding torque but won't give you continous positioning.

Brushless dc motors give continuous positioning that can have very low torque ripple, but you will need a controller and a position sensor.

Brushed motors are not going to be satisfactory at anything like 150degC.

In addition, the high temperature will almost certainly require class 200 copper wire, eg Kapton (polyimide), and avoid neodymium iron boron magnets.

 

[jclough]

We've done this sort of under the hood application before.

Feel free to contact me if you need help.

Jon

 

[rayclag]

The actuator needs to provide continuous control throughout the range of motion. From what I've seen, brushless DC motors appear to be the preferred solution in similar applications, however the system cost is high. (Motor+Hall Effect Sensors+Driver+Gearing+Position Sensor+MCU). The force and travel required to control the valve (about 110N and 10mm) eliminates proportional solenoids or torque motors from consideration.

 

[frankeng9]

Rayclag,

From the information that you have provided so far, a proportional solenoid actuator could provide what you are looking for (25 lbs force and 0.4 inches of linear stroke – correct?) in a package size that would probably be competitive with a motor/gear-train solution. Motors certainly have many advantages and a motor may be your best alternative in this application, however there are many applications where a solenoid can provide a more cost-effective solution. It all depends on the constraints of your project (size limitations, power consumption, etc. - most automotive applications are extremely stingy with the amount of power allocated to an “under-the-hood” electro-mechanical device). Solenoid actuators have provided solutions in ABS braking, active suspension, fuel injection, and fuel regulation where cost and a “fail-to-neutral or closed” condition is required.