DC motor control circuit

[MBfreak]

I am working on a buddies engine brake to automate it. It is a water brake and good for up to 1200 hp at 6000 rpm.
We want to put in an analog control system and I have most of it breadboarded and bench tested. Ramp generator, PID control , D/A frequency converter for speed signal, displays etc well in hand.
The water valve that adjusts the brake torque is a fairly simple valve, which makes it a handful to adjust precisely. A manual trial with a DC motor/gearbox gave promising results. But the backlash will kill the idea of precise manual control of the drive motor for the valve.
So I am now trawling the IC manufacturers datasheets trying to find an IC that can ;
Run a 12V 15 A commutator DC motor
Bidirectional
Analog input like -10V to 0V to +10 V for full reverse to standstill to full forward in a linear fashion ( ie + 5V = half speed forward) No speed feedback needed, current limiter would be nice.
Either a standalone signal/power unit or separate signal and power, eventually with outboard MOSFETs for the H bridge.

Have not found suitable stuff. Found LOTS of units that are controlled by a digital interface, but not ready for that yet. Found some "kits" that wouuld do it, but I am not a great fan of those, unless someone has a really good suggestion.

I am not into ARDUINOs or programmable digital electronics.I know it would be MUCH better but I am strictly analog when it comes to electronics. I want the control parameter equations to be identifiable by passive components assisted by opamps. Sorry, but that is the way I am.

All help much appreciated

Ola

 

[jgorm]

sounds like you need a servo and plc controller.

 

[_Dock_]

How do you have the gearbox connected to the valve? When you say backlash where axacly are you getting it at?

 

[justsam]

Have you considered using a stepper motr?
Can the valve be replaced with some proportional control valve?
Take a look at some of the servos used in radio control vehicles, however most today are digital or PWM

 

[MBfreak]

Electrical design issue solved by using a BurrBrown OPA 549. Old school, completely within my competence and benchtested. Will be part of the system when assembled.
The valve is of poor design, and so is the drive motor. I will leave that to my very competent buddy to sort out. He will probably make a new valve with a directly coupled drive. "Hydraulic" design will be kept but all parts will be new and machined to close tolerances. Plastic bearings will be replaced by metal design.

Ola