How does HICAS get YAW-RATE FEEDBACK in an R33????

[ACEMANN]

I have verified ALL HICAS signal wire functions, colors, and pin assignments. I also have a system schematic drawn in the R34 PDF format...much easier to read than the R33 schematic. Right now it is hand-drawn, but I will whip up an electronic one soon enough. Big thanks to Alex Au on SDU for letting me have the Super HICAS steering chapter for the R33...I won't be giving out the the chapter, but my custom schematic is easier to read and has much more info.

I have taken photos of the HICAS control module PCB's as well...maybe I can get some feedback on what you think you see. There are two big IC's with the same part numbers, but different "labels" (they have stickers on them with more ID numbers). I am trying to figure out where the yaw sensor is (be it a piezo gyro or the like) but it doesn't seem to be very obvious. I'll try to post pics later tonight...well, in the morning for you guys...

I have also obtained SAE documents on the Super HICAS system...it is VERY in depth (control algorithms are explained, system schematics) but it only covers the pre-electrical system, and no yaw-rate feedback systems are explained. However, it is very obvious that any type of yaw data fed back into the control parameters would greatly enhance the responsiveness and accuracy of the system. In addition to the SAE article, I have also obtained 2 patents for the HICAS 4WS system...once again, no electrical / yaw systems are mentioned, but it is extremely in-depth. All the articles are dated 1991 or earlier, and I couldn't find any HICAS information after those dates. I guess all the modifications to the system were kept in-house at Nissan and not disclosed.

Did you know that Nissan engineers wanted to incorporate a "Mild" and "Sport" setting for HICAS back in early '90? I didn't...it made me realize that Nissan must have made compromises to the system...it could be way more responsive, as the control algothims show a big difference in some of the constants used to compute the steering angles. Crazy stuff...

And if you are wondering why I am even doing this, well, I am going to install the yaw-rate feedback electric HICAS on my NA 300ZX. Don't flame...I have ALL hardware, and have already drawn the necessary schematics to integrate the system into my zed...power supply, fusing, relays, signal wires, etc, etc. I have also designed a custom wiring harness (nothing hardwired here...using AMP connectors). I am also going to incorporate my own "HICAS lock" by installing a switch for the HICAS system power...I can turn it off at will...EVERY part of the system, not just the actuator. This will come in handy if I have to drive on crap roads, gravel, or if I just don't want the thing on. Also, the way I designed the harness, it will be really easy to diagnose any missing or busted inputs.

I guess the big question is "Why??", and all I can say is "because I can" hahaha

PCB pics soon, as well as the schematics for you R33 guys that need some diagnostic info...

[Ant]

Wow, great progress. The body of HICAS knowledge has just been hugely increased thanks to your efforts!

AFAIK the electrically actuated HICAS was introduced with the R33 series (and 94+ 300ZX's?), it may be that when they redesigned the system to use the electrical actuation the yaw-rate feedback stuff was introduced at the same time? May explain why your pre-91 documentation doesn't mention it.

Putting the electric HICAS into your 300ZX - sounds like a very interesting project!

[GTRgeoff]

Cam, big effort. I think you may do ok with the electric HICAS as the motor and gearing should have enough feedback torque to resist movement when it is switched off/locked. There may still be a small amount of slop but that would be fairly small.

Regardless how clever Nissan tried to be, the fact remains that every track driver who has locked HICAS considers their handling more predictable after locking.

Do it because you can. I suppport you all the way and good luck.

[ACEMANN]

Wow, great progress. The body of HICAS knowledge has just been hugely increased thanks to your efforts!

AFAIK the electrically actuated HICAS was introduced with the R33 series (and 94+ 300ZX's?), it may be that when they redesigned the system to use the electrical actuation the yaw-rate feedback stuff was introduced at the same time? May explain why your pre-91 documentation doesn't mention it.

Putting the electric HICAS into your 300ZX - sounds like a very interesting project!

Yea, the electric HICAS was introduced in the '94 Z32's...but the system was not the same as the R33's. The control modules looked completely different, and there was never any mention of "yaw-rate" anything. What is even more strange to me is that they NEVER used the HICAS system from the Skyline in the Z32...they just stuck to the original system, albeit electric in later models.

[ACEMANN]

Cam, big effort. I think you may do ok with the electric HICAS as the motor and gearing should have enough feedback torque to resist movement when it is switched off/locked. There may still be a small amount of slop but that would be fairly small.

Regardless how clever Nissan tried to be, the fact remains that every track driver who has locked HICAS considers their handling more predictable after locking.

Do it because you can. I suppport you all the way and good luck.

Thanks for the complement...I agree with you, I should be ok with the HICAS actuator disabled as long as I don't drive too hard. From what I have read, most guys that do this get away with it without too many problems. Of course, I would only do it when necessary, and I could turn it on immediately...

As for your comments on HICAS and track use...I agree totally with what you said. Everything I have read (and personally felt) about HICAS was that the system was designed to give superior handling (high & low speed) on the street. Quick, high speed lane-change maneuvers, high speed stability, and more precise handling at moderate speeds (backroads anyone? :uh-huh: ) was what it was designed to augment. I wouldn't drive with HICAS on a track either...the actuators aren't fast enough, and the software just isn't written for the track environment.

It might be a month or so until I finish the schematics, but when I get them done I'll post them in a dedicated thread. Hopefully it will alleviate some HICAS woes...at least you will know where to look, and what wires to check.

[ACEMANN]

Ok, last post for today, but I ran into some really interesting info...I found more patents from Nissan that pertains to HICAS...electric HICAS...as well as another patent that dives in to the mathmatical models used. Here are links for the brave

"Vehicle Motion Control Apparatus"

http://www.freepatentsonline.com/5957987.h...ghlight=5957987

"Vehicle Steer Angle System Based Upon Mathematical Model"

http://www.freepatentsonline.com/4840389.h...ghlight=4840389

I have hardcopies of the following:

"Four Wheel Steer Control System"

http://www.freepatentsonline.com/4893690.h...ghlight=4893690

Development of "Super Hicas"--A New Rear Wheel Steering System With Phasereversal Control

http://www.sae.org/servlets/productDetail?...&PROD_CD=891978

Steering control system for wheeled vehicle

Contains info on the "Mild" and "Sporty" modes

http://www.freepatentsonline.com/4949261.h...ghlight=4949261

Be sure to check out the Patent References as well...most are linked to similar systems by Nissan.

Now for pics of the HICAS control module PCB's:

http://share.shutterfly.com/osi.jsp?i=EeAM2TdizcOHDgw

Just follow the link and click "view pictures"...you can view them individually or as a slide show.

For the curious, here are the part numbers to the two big IC's you see in the pics

Left IC

Sticker

19US

80

31022

Right IC

Sticker

19UM

80

31022

ID info on BOTH IC's

3K1 J

HD6475328CP10 Japan

Now, after reading all this info, pouring over schematics, and seeing the PCB first hand, I am in serious doubt (arrgh...again) as to the use of a "real" yaw rate sensor. There seems to be quite a bit of "feedback" (my god how many times have I said that word LOL...) of the orignial yaw-rate calculatons into other parts of the program AFTER the steering angle has been calculated...somewhat of a "check" in the system without sensor input...I might have that wrong...I dunno. Don't get me wrong, I don't feel as if I know everything about this system...really, the more I read the less I realize I know

But hey, makes for a fun summer project before school kicks up again!

Enjoy the info, and I look forward to any comments!

[ACEMANN]

The HD6475328CP10 semiconductor is a 16 bit microprocessor made by HITACHI...there are two of them on the R33 HICAS module.

Datasheet:

http://www.digchip.com/datasheets/parts/da...475328-CP10.php

I'm not seeing any piezo gyros or anything that could detect yaw motion...it must be recycling the calculations to fine-tune the output...???

[ACEMANN]

Found this on Nissan Japan's website, for the R34:

The picture is titled: Yaw-Rate Feedback Electromotive SUPER HICAS System Figure

It seems there really IS a yaw-rate sensor feeding data to the HICAS control unit...please note the cylinder-shaped object directly above the right-rear wheel.

By using an online translator, I have been able to determine that the caption for this "sensor" pictured above the right-rear wheel is a yaw sensor. The text comes to within 2 characters of a direct translation (English to Japanese) of "yaw sensor":

English: Yaw Sensor

Japanese: ヨーイングセンサー

Compare to the text displayed within the diagram

This diagram displays an undisputable implementation of a yaw sensor of some type, feeding the HICAS system directly.

After seeing this diagram I am even more confused as to how the system works...every schematic I have gotten my hands on (both R33 and R34) do NOT show ANY "yaw sensor" inputs of any kind going into the HICAS control module. That is why I assumed that the sensor must be on the PCB's themselves, but after a very thorough examination of the PCB's, there is obviously NO sensor of any type...I thought I had this cracked! :confused:

Opinions???

BTW...the two white boxes seem to represent the "target states" of the vehicle's yaw motion. The top box seems to be the "ideal" model (i.e. steering angle, vehicle speed) while the bottom box seems to be the more complex of the two. It looks like it takes the result of the first calculation, and feeds it into the second calculation, as well as taking into account the vehicle speed and steering angle once more. Finally, it takes the actual yaw motion of the vehicle via the yaw sensor and compares it to what was desired. I guess some type of really complex subtraction takes place to see what needs to be reduced or added (for the rear-steering angle)...OK, enough...LOL

Interesting movie for HICAS:

http://www.nissan.co.jp/STAGEA/M35/0408/ME...ECHA/main2.html

FYI, I also finished my schematics for the HICAS interface with my zed...should start wiring next weekend...woohoo!!

[sav man]

Does anyone know where the HICAS gets the VSS line from in a R32 GTR? Cause wire 53 has conectivity, but i want to test from the ECU to the HICAS unit, so if I could find what wire to test that would be great.

[ACEMANN]

Does anyone know where the HICAS gets the VSS line from in a R32 GTR? Cause wire 53 has conectivity, but i want to test from the ECU to the HICAS unit, so if I could find what wire to test that would be great.

I am not familiar with how the R32's system is set up...but I am trying to understand what you want to do. Is wire 53 on the ECU or HICAS control module?

You are right though...if you can verify the continuity between the HICAS control module and ECU, then you can rule out busted wires.

[sav man]

I have tested between the speedo and wire 53 on the ECU (commenly cut to get around 180k limit). But I want to test the link between the ECU and HICAS unit, and there is alot of wires to test, the Z32 should have the same HICAS unit (Z32 and R32 share afew parts) do you know what wire on the HICAS unit the speed sensor is?

[GTRgeoff]

It seems there really IS a yaw-rate sensor feeding data to the HICAS control unit...please note the cylinder-shaped object directly above the right-rear wheel.

After seeing this diagram I am even more confused as to how the system works...every schematic I have gotten my hands on (both R33 and R34) do NOT show ANY "yaw sensor" inputs of any kind going into the HICAS control module. That is why I assumed that the sensor must be on the PCB's themselves, but after a very thorough examination of the PCB's, there is obviously NO sensor of any type...I thought I had this cracked! :confused:

Opinions???

My thoughts, that "sensor" looks a lot like a stylized control motor on the hicas unit, and the hicas has a couple of pot style position sensors on it. Maybe they consider the rear steering angle to be the yaw rate when related to speed.

[ACEMANN]

I have tested between the speedo and wire 53 on the ECU (commenly cut to get around 180k limit).  But I want to test the link between the ECU and HICAS unit, and there is alot of wires to test, the Z32 should have the same HICAS unit (Z32 and R32 share afew parts) do you know what wire on the HICAS unit the speed sensor is?

Here you go:

http://300zx-twinturbo.com/cgi-bin/manual....efault&total=98

hope this helps...and as far as I know, the Z32 and R32 systems are the same (??)

[scathing]

Good luck with the conversion.

Considering your intended purpose and the rest, people would be foolish in wanting to knock you for installing a better HICAS system onto your car. If you're primarily street driving, the extra handling response and stability would be great. Not to mention a smaller turning circle for parking

After watching your Stagea link, though, I was once again reminded of the nice AWD driveline in the 35's. Just wondering how much it'd cost to fit the AWD and HICAS system out of the Stagea / Skyline into a Z33. Couple that with a TT kit and I'll go hunting Porsches.

[ACEMANN]

My thoughts, that "sensor" looks a lot like a stylized control motor on the hicas unit, and the hicas has a couple of pot style position sensors on it. Maybe they consider the rear steering angle to be the yaw rate when related to speed.

That is a good point...I didn't really take into account the diagram is really just an advertisement on how the system works...not a real world setup and definately not a REAL system diagram. Funny thing is that you should mention this now...I considered that the rear steering angle sensors might be utilized for yaw calculations, but I just assumed they were used for motor control feedback. Another reason is because the Z32 has a similar actuator (electric of course), and it has two rear-steering angle sensors as well (steering angle main and sub-sensor). I thought "Why use these sensors when Nissan can design a control unit with gyros, etc"

Well, this patent made me think different:

http://patft.uspto.gov/netacgi/nph-Parser?...=hicas&RS=hicas

Quote from above patent

"In the instant embodiment the variable steering characteristic controller 19 can take the form of the rear wheel auxiliary steering device which is referred to as "Super HICAS" and which is disclosed in Nissan Skyline RS32 type vehicle Service Manual No. 622 pages C-97 to C-104 (published in May 1989) and English language publication entitled: NISSAN SUPER HICAS (EO-2000-8908). "

This statement means nothing until you realize that the patent I just linked is for a Traction Control System that is spec'd to use either rate gyros or g-sensors to detect deviations from the desired path.

This patent is really for a "Yaw-Rate Feedback" Traction Control System...if HICAS is indeed substituted, then you have "Yaw-Rate Feedback" HICAS.

And what is a major problem with the older HICAS? In some situations it begins to produce understeer, because there is no way for the HICAS system to recognize if the "target yaw rate" is being held. Read the abstract for the above patent:

"In order to prevent a traction control system and an auxiliary steering or the like from combining stabilizing effects in a manner which causes excessive understeer, when the traction control is functioning in a predetermined manner, a signal is issued to the auxiliary steering control and reduces the gain with which the control thereof is implemented. As a result excessive understeer is avoided while maintaining suitable vehicle stability."

Now, this is what changed my thinking as to how Nissan would gather Yaw data:

"It is further possible to use the outputs of the wheel speed sensors and to derive the vehicle yaw rate in place of the rate gyro 17 if so desired. In addition, it is possible to use the difference between the actual and target yaw rates for feedback control purposes and use the same to derive the duty cycles of the signals which are used to modify the amount of torque which is permitted to be transmitted to each of the driven road wheels and thus enable the division of drive torque therebetween to be controlled."

So, they outline using either G-sensors, Gyros, or the wheel speed sensors to derive the vehicles actual yaw-rate. They don't mention using any type of rear-angle sensors, but knowing that there are NOT two distinct wheel-speed inputs into the HICAS control module leads me to believe that another method must have been used. The simple fact that so many methods were proposed to compute yaw rate, right down to using wheel speed sensors, makes me realize that the engineers were pretty open to using any option available to gather that data...this proves that they did not limit themselves to using expensive gyros.

Whew...enough typing, but I seem to be closing in on how this system works. Maybe someday HICAS won't be such a big mystery...

[ACEMANN]

Good luck with the conversion.

Considering your intended purpose and the rest, people would be foolish in wanting to knock you for installing a better HICAS system onto your car. If you're primarily street driving, the extra handling response and stability would be great. Not to mention a smaller turning circle for parking

After watching your Stagea link, though, I was once again reminded of the nice AWD driveline in the 35's. Just wondering how much it'd cost to fit the AWD and HICAS system out of the Stagea / Skyline into a Z33. Couple that with a TT kit and I'll go hunting Porsches.

lol...that would be pretty sweet. I have no clue as to how much that would cost...just finding the parts would be hard enough. I haven't seen too many G35x's running around, let alone wrecked already. Does the Stagea have the FM platform as well? I didn't know that. An AWD/4WS TT Z33 would definately kill some Porsche's, and maybe a Ferrari or two

[scathing]

From the pictures of the suspension that they have posted (which admittedly is only from the "outside" shot) its identical to a Z33's. Which means there should be clearance to run those front driveshafts. The Stagea has always traditionally been a "Skyline wagon", so them sharing the same platform isn't unsurprising.

Of course, there's the small matter of if there's enough room for the driveshafts and turbochargers, since I'd hazard to guess that they'd be attempting to occupy the same space.

The APS TT kit on a RWD Z33 puts out 300rwkW, which is about what a 996 Turbo makes at the flywheel. Unless the Nissan ET-S system and twin turbo kit weighs a lot more than the 50kg difference between the Z33 and 996, the Nissan would still have a power advantage.

It'd probably cost 996 Turbo money to get it all sorted and reliable, though, but it would wipe the smirk off a lot of Euro car owner's faces.

*sigh* If only my dreams were as attainable as your dream of upgrading your HICAS.

[Ant]

lol...that would be pretty sweet. I have no clue as to how much that would cost...just finding the parts would be hard enough. I haven't seen too many G35x's running around, let alone wrecked already. Does the Stagea have the FM platform as well? I didn't know that. An AWD/4WS TT Z33 would definately kill some Porsche's, and maybe a Ferrari or two

The WGC34 Stagea (96 - 01) is based on the C34 Laurel platform, which is also the basis for the R33 platform. Drivetrain is basically the R33 system.

The M35 Stagea (01 - current) is essentially just a wagon version of the V35 Skyline/G35. So platform is identical AFAIK.

If my impression of the new GTR rumours are correct, then it will answer your prayers - will basically be a TT (engine displacement still unknown) V35 (probably V36 by the time it comes out) coupe with the ATTESA and maybe HICAS as well.....

Re the yaw sensor stuff - you're making my head hurt again..... Haven't had time to wade my way thru the links you've posted, but when I do I'll post up my thoughts...

I thought you'd cracked it with the fact it might use discrepancy in individual rear wheel speeds to derive the yaw rate - very clever. But you're right, only 1 VSS input - doh!

[ACEMANN]

IT WORKS!!!!!!!!

SUCCESSFUL INTERFACE BETWEEN R33 YAW-RATE FEEDBACK ELECTROMOTIVE SUPER HICAS AND Z32 FAIRLADY!!!!!

MANY PICS SOON!!!!

yea, I'm a little happy :uh-huh:

-Cameron

[sav man]

Is there any noticable diference in the handeling of the car?