How can you lock the rears?

[peanutaxis]

From Wikipedia:

"For example, an irrigation sprinkler system, programmed to turn on at set times could be an example of an open-loop system if it does not measure soil moisture as a form of feedback. Even if rain is pouring down on the lawn, the sprinkler system would activate on schedule, wasting water."

A diff would then be open loop as the input comes from a human. Traction control would be closed.

[autogyro]

From Wikipedia:

"For example, an irrigation sprinkler system, programmed to turn on at set times could be an example of an open-loop system if it does not measure soil moisture as a form of feedback. Even if rain is pouring down on the lawn, the sprinkler system would activate on schedule, wasting water."

A diff would then be open loop as the input comes from a human. Traction control would be closed.

Hmm, surely the time control over the sprinkler valve makes it closed loop not open loop?
I dont think the human comes into it a great deal these days.

[raymondu999]

From Wikipedia:

"For example, an irrigation sprinkler system, programmed to turn on at set times could be an example of an open-loop system if it does not measure soil moisture as a form of feedback. Even if rain is pouring down on the lawn, the sprinkler system would activate on schedule, wasting water."

A diff would then be open loop as the input comes from a human. Traction control would be closed.

Open loop = NO external input & feedback
Closed loop = WITH external input & feedback

It's raining. You have a sprinkler on a timer.
Open loop = sprinkler turns on in rain
Closed loop = sprinkler detects rain and turns off

It's a diff at 50% lock. You have a driver on the throttle and steering.
Open loop = diff lock stays at 50% no matter what throttle and/or steering input is provided
Closed loop = diff lock can change as drivers steer and throttle

[Tim.Wright]

It's a diff at 50% lock. You have a driver on the throttle and steering.
Open loop = diff lock stays at 50% no matter what throttle and/or steering input is provided
Closed loop = diff lock can change as drivers steer and throttle

That's still not closed loop because there is no feedback.

Closed loop has to measure something at the output (like wheel speed, or slip ratio or yawrate) and then use that as a part of its setting of the diff locking.

Steering angle and throttle demand are inputs given by the driver not outputs. They don't tell you anything about what the car is currently doing.

[rjsa]

May be the engine will stall and it will jump start once the wheels get moving again.

[xxChrisxx]

People above already explained closed loop better.

[rjsa]

It's raining. You have a sprinkler on a timer.
Open loop = sprinkler turns on in rain
Closed loop = sprinkler detects rain and turns off

Wrong.

Open loop: It's raining. You have a sprinkler on a timer. Sprinklers run for 30' on dry and turn off in rain.


Closed loop: Sprinkle system has a sensor that will shut it off or prevent it from starting if soil humidity is at target value. It might or might not start under rain according to the variaton of humidity in the last 2 hours.

[autogyro]

http://www.youtube.com/watch?feature=pl ... xig8iM7jDU

Open loop closed loop???

[rjsa]

There is an interesting theory in some other post around here describing how with a couple of electric/electronic components you could turn the KERS charger system into and engine damper. That would be indeed a closed loop control system that could ha such a result.

[Tommy Cookers]

There is an interesting theory in some other post around here describing how with a couple of electric/electronic components you could turn the KERS charger system into and engine damper. That would be indeed a closed loop control system that could ha such a result.

the KERS and the 2014 ERS can both either as motors or generators
for each and every possible motor/crankshaft rpm (they are geared together) there will be a level of voltage specific to the rpm
when MG energisation is below this voltage the MG will load the ICE and car and generate proportional to the voltage defecit
when MG energisation is above this voltage the MG will drive the ICE and car and consume electrical power proportional to the voltage surplus
at every moment the MG drive 'knows' the MG rpm so it can apply an appropriate voltage for the desired level of motoring or generating

under drive, wheelspin makes rpm suddenly rise, the motor torque will automatically fall without change in motor energisation voltage (because the rpm rise has caused the voltage surplus to decrease)
under braking wheel locking makes rpm suddenly fall, the generator load will automatically fall without change in energisation voltage (because the rpm fall has caused the voltage deficit to decrease)

so there is within the motor drive (ie passively) a natural inherent effect acting against both wheelspin and wheel locking
it would be hard to avoid such an effect (it is basically the same effect as occurs in a model railway)

also it would be very simple to apply (even within the drive) a ripple to the MG energisation voltage
that would produce a torque ripple to the wheels
traditional belief has it that a torque ripple will give more grip
the controller could also do this (better)

all this would appear to be legal, as it doesn't involve wheel rpm sensing

[rjsa]

I've read an explanation that I can't repeat of capacitors and other stuff actually working as a derivative control. It made sense but I'm not able to judge since I know squat off electronics and high power electricity.

The pulsing is what Senna used to do, right?

[Tommy Cookers]

there will be an rpm transducer (a tachogenerator or similar)
this could be providing a derivative of the nominal controlled variable (internal to the drive of course)

the effect in the clip could be accidental (or engineered)
the car's resonance in surge on its tyres being excited by instability of the motor/load combination at that periodicity

there's a recent/current thread elsewhere on this behaviour ?

[rjsa]

There you go...

KERS analog TC system:

Activation and "control" of the KERS systems are digital.

The system itself has to be analog in nature.

You incorporate a "voltage over run" circuit, to prevent "over discharging" the batteries. You do the math on determining what the rpm is in 1st or second gear, and you make an *analog* circuit that not only cuts the battery output based on a lack of back-EMF from the motor, but also ramps the energy down/up depending on the impedance coming from the motor. If the tires are slipping, the motor suddenly over runs, the circuit cuts power. You can do this analog with capacitance, and all sorts of pre-21st century ways of getting D/C rectification. The ECU would only know that it's asking the circuit to supply X amount of voltage/time, but the circuit itself could have EM properties the ECU (and the FIA) doesn't have to know about.

The way you design the circuit to oscillate the energy up and down would be optimized for a certain RPM/impedance, and it wouldn't be seen in tire marks - unless an oddball combination of factors happened (car acceleration angle vs. CG). A more squared off acceleration angle might hide the frequency of the ramping, but under the right turning angle/acceleration might reveal itself as a function of the tire diameter/f.

So, the motor itself is the TC "sensor" and it's simple enough to disguise a "voltage over run" circuit to do what I describe - it's basic analog electronics. "KERS ballast". The ECU wouldn't have to know or show the results of it. You could maybe make it driver controllable by disguising it as part of the harvesting function, by allowing the driver to place his foot on the brake?

/ $.10

http://www.f1technical.net/forum/viewto ... 68#p437268