Sunday, January 14, 2018

Fun (?) with an AJA Cion

Long camera is long
It was Black Friday 2017 and I hadn't bought anything. Thankfully, the fine folks at LensAuthority were running a special on the AJA Cion, an oft-maligned CMV12000-based camera  It was real cheap, cheaper than a CMV12000 machine vision camera, and probably more ergonomic as it had the capability to record ProRes internally to proprietary or Cfast 2.0 media at 60p.

General Impressions

You probably don't want this camera for general cinematography; the sensor is noisy enough that you will be spending a ton of time fighting the camera. For example, a simple interior shot of MITERS proved to be too much for the sensor, and MITERS is not exactly a high dynamic range scene. This is further compounded by the fact that the noise is heavily patterned; some rows are noisier than the others (not to be confused with FPN!), which is a lot more distracting that having white noise distributed over the image. And forget about available light shooting, the only ISO you get is 320 (500 and 800 are a joke, the sensor has little enough DR even with no gain applied). Folks can go on about 'great color science' and 'ready to edit codec' all they want, but it is hard to justify a $5K camera with barely 10 stops of dynamic range when the Ursa Mini 4.6K falls in the same price class and is so much better at everything.

The adequate. The fact that the menus don't show up on the monitoring outputs really puts a damper on operation, as the operator cannot see the settings while the camera is rigged up and shoulder mounted. Even on a tripod, using the click wheel to scroll through 30 menu entries is unpleasant, especially when you can only see one row of the menu at a time (come on AJA, give us a firmware update that fixes this!). Thankfully, operation is very slick when the camera is tethered through an Ethernet cable and operated through the browser interface - the embedded website is intuitive and, more importantly, doesn't seem to exhibit the inconsistent hangups and crashes that plague a ton of my other Ethernet controlled gadgets.

The real strength of this camera, in my opinion, is as a specialized, tethered camera. 4K120 raw is rather state of the art; no other "consumer" camera on the market can do this (RED and Kinefinity can do high framerate wavelet-compressed recording though). As for capturing the HFR output...

Raw Recording

...I'm not sure how I feel about quadruple SDI based output. On the one hand, SDI capture cards are readily available and well-standardized, and I would certainly take four BNC's over one CameraLink cable any day. On the other hand, multi-tap SDI capture is a mess right now (not all cards support combining their inputs out of the box), and RAW transport over SDI is basically a scam, with recorder vendors charging hundreds of dollars for the software licenses to enable RAW recording for each supported camera model.

Image from AJA's site
The only officially supported ways to record the 120p output are via a device called a 'Corvid Ultra' (some sort of $20K box that plugs in via Tesla-style PCIe HIC's), or using an AJA Kona4, a $1995 quad 3G-SDI capture card. The Kona software (AJA Capture Room) has a preset for CION RAW (confusingly enough, the button in the software is not where the manual says it would be). This seems to set each tap as 2K60p, so presumably each frame from each tap encapsulates two consecutive quarter-frames of the full image. It should be possible to record the output as four uncompressed 2K60p Quicktime files on several third-party capture devices, then merge the frames in post; unfortunately, as of this writing there are no small 60p-capable SDI capture devices - all models available have an integrated monitor.

The officially recommended hardware to capture 120 FPS raw is absurd: start with an HP Z820 and a pair of LSI 9721, each equipped with four Intel S3700 or six (!) Intel S3500 drives in RAID 0, then stripe the two RAID 0 volumes together (!!) in Windows to create one large virtual drive. Come on guys, even when the release notes were last updated (2015), NVMe drives and 3D NAND were a thing. I also don't understand the suggestion to use enterprise drives; clearly, if you are running octuple RAID 0 across two RAID cards, you've given up any hope for reliability. A single OCZ RD400 or 960 Pro (512GB or higher) can handle the throughput (even when the drive is nearly full), and a pair in RAID 0 should more than do it. Or, if you feel bleeding edge, a single Optane drive should be able to do it with unbelievable consistency.

For the sake of size, my recording box uses a i3-7100 and a single 512GB RD400 drive; the rather low-performance CPU seems to be OK for Capture Room (which uses a whole core to debayer the preview but otherwise doesn't consume much CPU power). 512GB was chosen as the minimum size needed to achieve the requisite worst-case write speeds, but offers an incredibly mediocre six minutes of recording at 120 FPS. It is important to note that Skylake/Z170 is the oldest "small" platform where the chipset PCIe ports are PCIe 3.0 - anything older and you risk degrading the recording drive's performance.

Capture Room

AJA Capture Room is...very good. This was unexpected, as I am used to very expensive scientific hardware shipping with LabView or Java based garbage that makes your computer feel like its from 1999. At least on Windows, the UI doesn't feel as native as I'd like it to be, and sorting out the dozens of configuration options for the Kona4 requires reading a PDF manual, but I haven't had a crash, and more importantly, it can extract the full performance of the SSD. A lesser program would require 2x overhead to be able to run properly, but clearly someone at AJA actually cared about performance.

Image Quality

(or lack thereof)

Cinema DNG processed to taste in Capture One
The above test scene was shot on a 24mm Art at f/1.4 and processed as a still in Capture One. Exposure was 360 degrees (1/120) and 120 FPS. The primary defect that stands out is the noise in the background; the scene was processed with a 'flat' tone curve that boosted the shadows a substantial amount. The banding (which is caused by the read noise being spatially correlated, not "fixed pattern noise") is incredibly distracting; it is visible in the resulting video as a bright lines scrolling vertically in the shadows. That being said, the colors look beautiful, and you could easily shoot this scene with some fill light and avoid the noise problem altogether.

The other problem is Resolve doesn't process the RAW's nearly as well as C1 does, as it uses fast GPU implementations of pretty basic algorithms. For example, the only sharpening available is a simple unsharp mask; there is no attempt to intelligently detect structure in the image, resulting in sharpening being unusable in the presence of noise. Is the solution to output JPG's from Capture One into Premiere Pro? Probably not; having a program which natively handles raw video is amazing, and so much less clunky than a cobbled together stack of software.

Monday, October 23, 2017

Naked Go-Kart

The big go-kart came apart for some cleaning, re-painting, and general beautification recently; this was also a good opportunity to get some shots of a relatively uncluttered frame for documentation purposes.

What a contraption. Towards the back you can see the Polychain GT Carbon drive, which has replaced the old multi-V belts.

Such Art (24mm, to be precise)

Sunday, October 1, 2017

2016 (Third Generation) Smart ForTwo Electric Drive Drive Unit Teardown

In addition to the Leaf drive unit, we recently acquired a Smart ForTwo drive unit. This one is somewhat of a unicorn - there are no images available, and little information other than it uses a Bosch SMG 180/120 motor and is 55KW. It is also of particular interest because the SMG 180/120 is an off-the-shelf motor and therefore should be easy to integrate into other vehicles; in addition, it has a distinguished heritage, being used in such applications as the Fiat 500e and the front axle of the Porsche 918.

Pre-shucking drive unit shot:

Integration is...poor. This makes sense since the Electric Drive was never a high volume vehicle - it was probably a compliance car designed to boost Mercedes' fleet mileage, and relied heavily on subsidies in EV-friendly states to break even.

Donor vehicle's tag, for future reference:

First, a diversion - the air conditioner compressor:

The compressor is fully integrated - DC and CAN in. Internally, it is a scroll compressor:

and an interior PM motor:

with a small inverter mounted to the back. Useful? Unlikely, unless you need an 370VDC air conditioner.

Time to move on to the meatier components. The integrated charger is a 6.6KW unit made by Lear:

Once again, severe coolant draining was required before we could proceed further:

Once the coolant was drained, the charger came off with a few bolts, revealing a nice self-contained unit:

We didn't look further into the charger, as we had minimal interest in turning it on, but it shouldn't be too hard to get running. Of note - the charger doesn't manage balancing, only AC-DC conversion.

Let's look at the inverter next. Aha! A part number! The inverter is an EFP 2-3, made by Continental and sold by Zytek.

A little bit of digging shows that it is a 235A continuous, 355A peak unit. A handful of bolts releases the inverter from the rest of the unit:

Very small and cute. The HV cables probably weigh more than the power electronics.

At this point we had released the motor-gearbox unit from the rest of the drive unit. Already looks promising - nice round motor, practically movable by a single person.

Hi Charles!
After splitting the gearbox from the motor...

...we are left with the most adorable little traction motor:

The mounting pattern is very convenient:

Though dangling the 32kg motor off of those tabs is probably less than wise.

The gearbox is almost identical to the Leaf's, just smaller:

Internally, it is very similar:

We attempted to look inside the inverter next. It started out promising:

Oh hey, pin-style channels, presumably to reduce pressure drop.

The HV cable harness is...

...plugged in via giant blade terminals?!

Unfortunately, at this point we were defeated - the inverter housing had some concerning ribbon cables running to the internal boards, and it was very unclear how to split the housing without tearing up the cables.

Overall, this drive unit is very promising for small vehicle conversions. The poor integration is a blessing, as everything has sensible mounting holes, and there's a slim chance that it is possible to acquire the datasheet for the inverter and motor from their respective OEMs. Unfortunately 55/80KW (the latter is Bosch's peak rating for the motor) and 200Nm is not enough for a full car conversion - you would need a pair of them to get good power.

2013 (Second Generation) Nissan Leaf Drive Unit Teardown

We recently came across a Nissan Leaf drive unit:

Not shown: CHAdeMO charger blob
and of course had to look inside.

First, some outside dimensions for reference:

The drive unit is highly integrated; for example, the motor phase connections are short busbars:

Removing the dozen-odd screws and the three terminal screws allows us to separate the inverter from the motor...

...resulting in a very strange-looking U-shaped motor.

Pulling the next dozen bolts holding the differential and gearbox to the motor separates the gearbox from the motor:

A few more shots of the motor:

The natural next step was to look inside the gearbox...

...which unfortunately meant draining a liter of suspicious red Nissan Leaf fluid out first.

After that, it was simple enough to remove yet another dozen screws and split the gearbox housing:

Nothing much to see here, standard single stage helical gear going into an open differential. More pictures:

Overall reduction is a little over 8:1.

Next we look inside the inverter. First, a quick look at the waterblock channels:

Nothing to see here, standard cast channels.

Cracking the power electronics enclosure open required breaking through a lot of RTV sealant...

...revealing the gorgeous (and never-before-seen!) innards:

The inverter is much less dense than we had anticipated; the IGBT's have their own module (rather than being brazed straight to the waterblock), and there is a lot of empty space over the PM.

Controller is unfortunately based around a datasheet-less Renesas microcontroller, as are all Japanese automotive electronics.

Capacitor is 1088uF, 600V, SH film:

And a lot smaller than the one inside the 2nd-gen Prius.

Few more shots, including gate drive power supplies:

Overall, very well integrated with few surprises. I would not even dream of reprogramming this inverter, as dialing in the motor tuning for something this large would be very involved. My one comment is that this motor is probably good for much more than 80KW peak - judging by its size I would venture to say it is a 200KW-class motor.