i am working on a project in which i need to control motion of two
cylinders simultaneously and also need to keep their motion free during
valve ports blocked. the pump i am using is of low capacity and i also
need to add an accumulator to the circuit. can anyone give me advice on
how to synchronize the cylinder motions by using low-cost DCVs and Pr.
Regulating valves. i also need advice on sizing of accumulator and
Position feedback, proportional control valve (or a servo valve,
which requires high pressure and very good filtration).
3-way valve on each cylinder port.
Why? To "store" capacity for a while?
For accumulator and reservoir sizing, go to a hydraulics
professional. It isn't rocket science, but you haven't given
*us* enough information to help you.
What do you mean by "DCV"? I have used "temposonics" in
balancing 4 ton tanks of various fluids between just two
cylinders (think hammock).
You will get no sort of positioning control with a pressure
regulating valve, unless you have a spring in the cylinder. If
you have a spring in the cylinder, it won't be "keep their motion
David A. Smith
i am working on roll control system development for a Sport Utility
Vehicle. i am supposed to use the power steering pump in the initial
stages. the system works in parallel with anti roll bar to additionally
stiffen the suspension and thus achieving the roll angle reduction.
During a straight drive this roll control system is supposed to be
inactive (i.e. free floating) As the pump used is power steering pump,
to fulfill the flow needs of the actuators i need to install
accumulators in the circuit. also for concept proving we are trying to
use solenoid operated direction control valves (DCV)
i hope you might give me some advice on this situation.
Is this a school project?
Better to compress the inside shock(s) / extend the outside
shock(s), making the vehicle roll into the turn.
Note that as the power steering pump is also largely inactive in
straight line driving, you really will be taxing its capacities.
OK. The reservoir of the power steering pump needs to be
increased to hold the volume of oil held by the total of the
accumulators. Now for the bad news. The power steering pump
runs at very low pressure in straight line driving. Your
accumulators won't charge. You need a dedicated pump, in my
Thanks. It is always a good idea to define acronyms before you
use them. It is a Good Idea (IIAGI).
Stiffening the suspension only serves to remove any hint the
vehicle is in trouble. The driver can oversteer and have no
ability to recover because he can't read the roll angle of the
Better still, automatically apply the brakes if an SUV even
requires "automatic" turning assitance. Anyone that drives one
fast through a turn is trying to die. Off road ability and high
speed do mix, unless you are a jet.
Just my opinion.
David A. Smith
Using the power steering pump could overload it, or over heat it's oil.
It's desined for "intermitant use" when the steering is central it's just
idling as the rack alows the oil to bypass, any attempt to intercept this
low pressure flow would mess up the control system of the rack.
( it works by blocking the flow partly diverting it to the left or right
side and relies on a constant volume flow ).
Is the method of roll reduction going to require a large actuator effort, or
will the oil pressure simply be giving a control type signal ( tipping the
roll bar mounts with a jacking cylinder, or driving a pin valve to shut a
restrictor in a shock absorber )
Another possible hazard.. could pressure pulses genetated by a road wheel
hiting a bump feed back to the power steering and kick the steering ?
How would your system work in a skid situation if a driver applied negative
steering lock ? would it be trying to flip the car ???
firstname.lastname@example.org wrote in news:1141212144.679670.159160
In addition to what the other two posters have said, DCV valves would be
a bad choice, as they are either on or off, and the change is very sudden
in either direction. Also, most are not rated for rapid, continuous use
as I imagine could be the case in this situation. You would be better
off with an electronic proportional valve, which are fast reacting and
made for continuous variable use. Vickers, Bosch, Parker, and Moog are
the OP specified " low cost DCV valves ", The last time I looked the
proportional valves where expensive, especialy in the size required to drive
cylinders of suficent power to affect the roll of a car.
Having said that, I think you are correct in saying that proportional valves
are probably needed. Sometimes there is just no cheap way to get a job
done... especialy when human safety is involved.
Dear Jonathan Barnes:
You can actually get proportional performance from smaller,
cheaper valves. But then your electrical requirements go up,
since you are running them with PWM power supplies.
David A. Smith
hi to all,
as you pointed out i am not going to burden the powesteering pump. to
simplify the things our suggestion was to disconnect the powersteering
circuit and simply use the whole pump flow for this roll control
now as this project is running on low budget and we have to prove this
concept first so as to allocate more funds, we have no option but to
use solenoid operated direction control valves.
as far as roll system is concerned we are trying to use linear
hydraulic actuators inbetween the chassis and lower wishbone to provide
additional resisting force for the rolling action. the actual
displacement needed for these actuators is only 40mm. but we have to
use actuators of strokelength @ 140 mm to accomodate the complete
travel of the suspension in reboun and bump. also the forces
encountered were of the magnitude 3000 N and pressures encoutered in
the system are 45-46 bar max.
email@example.com wrote in news:1141362682.432671.193070
While fully realizing the low-budget deal, I have a feeling you are going
to introduce some unexpected problems by using DCV valves, from what I
understand from above, you are are basically going to use this as a shock
absorber. You are possibly either dumping flow from the cylinder into a
dead-head state, or possibly through a flow control valve or system.
Better still, add a second pump. Have you ever tried to steer a
vehicle set up for power steeering, but with the pump not
On a "bump" it will be higher.
I'd recommend you consider air shocks, an air compressor, and a
receiver tank. No "water hammer" effects to account for, pretty
responsive, and already in a key place to allow them to do what
you seek. The compressor can simply keep the receiver tank
filled, and be powered elecrically. You will need position
indication... as well as some sort of tilt sensor. Schaevitz
made one that was really cool.
i am not vehicle dyanmics expert so i may be making mistakes in
judgement. can anyone suggest me about the references to be studied
before plunging into this suspension related project work. i also came
across some papers on the active roll control system from Cambridge
Vehicle Dynamics Consortium (CVDC) but those are mostly related with
heavy commercial vehicles. can anyone knows about research papers
related to Active Roll Control in SUVs?
hope to see you all soon
You can write it when you are done.
A typical SUV will have similar suspension to a "heavy
commercial" vehicle. The time constants will be smaller/shorter.
The necessary instrumentation and controls will be similar, with
an increased response time. Less total forces will be required.
You need to stop "looking outwards". This is your task. You
have not accepted the advice you have been given. You either
want to do it yourself, or you are looking for someone to hand it
all to you free.
If you are ever looking for a small 12vdc electrically powered
hydraulic power unit with integral reservoir, Oildyne (which has
also been agglomerated by Parker) is a good choice for a research