"Drive by wire" suggestions

[ETBISME]

Hello All!!

I am currently working on a slow moving (15mph max) off highway vehicle that has a tandem pump directly coupled to the engine. There are two operator control levers connected to the pump via mechanical linkage.

I am trying to eliminate vibration transmitted from the pump/engine to the control levers. One option I am considering is some sort of "drive by wire" configuration (possibly microcontrolled servo or stepper motor?). Can anyone tell me if this can be done economically and possibly list some resources? Everything I have found seems to be for expensive industrial motion control systems.

Some of the initial design parameters:
+/- 21 degrees of rotation (42 degrees total travel) to control each pump input shaft
Actuate the full range (42 degrees) within 1 second
requiring around 10-15 ft-lbf
12 V DC electrical system
Harsh conditions including engine vibration and some moisture

What do you guys think? Is a servo/stepper motor system a good option for this application, or am I missing something. Any info or ideas will be greatly appreciated.

 

[MikeHalloran]

Ask at your local junkyard if they have a recent Corvette.

I think they have a drive by wire throttle.



Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

That is really easy EBUSSEN in principal..

Problem is "what is cheap enough" for you? And what technical abilities do you have? And are these just move fully here - move fully there, or some sort of turn just barely to this point and change the point according to some system result.

The cheapest solution, if you are just moving to a fixed repeatable position, is to use cable actuators to remove the vibration problem.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Look at thread 237-175346, and Clyde38's link.

http://www.aeroflex.com/products/motioncontrol/torque-intro.cfm

If you like it, don't forget to give Clyde38 a star.
respectfully

 

[ETBISME]

Thanks for the info and links.

Itsmoked, I am actually in the process of assembling a cable actuated system. However, I would eventually like to prototype a model that eliminates the mechanical control levers in favor of a "playstation controller"

Movement of the pump input shaft controls the speed and rotational direction of a hydraulic wheel motor. Therefore it is not a "move fully here to fully there" situation.

Correct me if I'm wrong, but I think my basic setup will involve 1) servos to control pump input shafts 2) A main control system to tell servos what to do and monitor sensors 3) input sensors to detect operators desired action, 4) another sensor to detect the machines actual action

My technical abilities are definitely not up to par for what this project will probably turn out to be, so if anyone knows of any servo control kit...let me know

Allowable cost for a production run...a few hundred $. For this prototype...under 1000.

 

[DaveScott]

Another way of doing what you want is to get pumps that automatically control pressure, and then use proportional hydraulic valves to control flow rate. Then you can control the flow rate using some small electrical signal (0-10V) which can be controlled by a joystick.
Cost? no idea.

 

[waross]

This sounds like variable displacement pumps. They can be used for automatic pressure control, but why bother when the variable displacement control is right there and does the job fine. They also give bi-directional flow. The motor ports are typically connected directly to the pump ports. Push the little lever forward and go forward, pull the little lever back and go backwards.
respectfully

 

[itsmoked]

Allowable cost for a production run...a few hundred $. For this prototype...under 1000

Well that's pretty a pretty good budget!

Just use a gear drive motor that is reversible.

There are some in automotive land that are cheap and integrated.

Examples:

http://www.allelectronics.com/cgi-b...VDC_GEARHEAD_MOTOR_(RIGHT-HAND_VERSION)_.html

http://www.allelectronics.com/cgi-bin/item/DCM-249/400/POWERFUL_WINDSHIELD_WIPER_MOTOR_.html

http://www.allelectronics.com/cgi-bin/category/400400/DC_Gear_Motors.html

There's Jameco too:

http://www.jameco.com/webapp/wcs/st...06|9&f1=706|15&f1=706|24&action=Update+Filter

You can use one of the windshield wiper species. You may get the translation aspect for free! Use a short cable to your motor actuator. Run the motor back and forth by reversing the DC leads.

You can go different ways by using a joy stick to dink it to position or an H-bridge for micro control.



Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hi Keith;
This would work but it makes me a little nervous. On a vehicle drive, I prefer a fail-safe arrangement. You don't want to have a wire come loose and find that you can't stop.
Respectfully

 

[itsmoked]

Isn't that when you jump out and the vehicle goes off a cliff and explodes as soon as all the wheels clear the ground?

Actually just turn the prime mover off, the thing will probably come to a quick stop. (?)

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[GregLocock]

Windscreen wiper motor, two pots and a comparator circuit, per channel. You could probably find details in an amateur robotics book.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.