[mira9_cz]

Hi Bigmouse. What an impressive idea with the Lexus hybrid gearbox! I spend last two days reading everything I found about your gearbox, they are motivationally inexpensive and available to buy. I can see that controlling motors independently will be quite a pickle. When they made the gearbox, they did not know that one day somebody removes ICE and fix input shaft

By locking ICE input shaft of the transmission you will fix the generator (MG1) with ravigneaux gear system output through primary output shaft. So If I understand correctly, RPM of MG1 will be proportional to vehicle speed in some ratio of locked power split planetery gearbox.
On the other hand motor MG2 is connected with rear wheels indirectly using two "gears" of ravigneaux system. I found that these gears can be MG2_RPM/1.9 or MG2_MAX/3.9. Does the MG1 ratio of locked Power split planetary cover both those gears of MG2 fully? Isn't there a "gap" at the beginning caused by locked input shaft from ICE?

I also wondered how gears of ravigneaux gear system are really shifted? You say that hydraulically by external electric oil pump. But how do you activate them? Simply by rising hydraulic pressure, or is there some CANBus line running between transmission and transmission ECU which operates some valves? Also it makes me wonder how Neutral and Reverse gears are shifted.

From what I understand up to this point, you can make clutches to move actuators by some manual input from driver. In the best case you will have to shift "MG2 LOW" gear only for burnouts, if MG1 will cover normal acceleration power-needs up to the point when MG2_RPM/3.9 are not too low to make the difference. Or you could make MG2 to shift HIGH and LOW gear automatically I guess based on realtime MG1 current, RPM and throttle inputs calculations. In both ways the gear changing issue is crucial for your MG2 motor controller programming. What is your approach here? At least is seems that recuperation braking for MG2 is not necessary to be considered

 

[bigmouse]

Hi Mira,

You are correct that locking the input shaft gives MG1 a fixed ratio (2.6:1) to the output shaft. There is no shifting of MG1. According to the LS600h ORNL report, MG1's rotor stampings are identical to MG2 in the Camry hybrid. The top speed of MG2 in the Camry is 14,000rpm, so I am assuming MG1 in the Lexus has the same top speed. It covers the entire speed range of the car and is, in fact, the limiting factor for the top speed of the car.

MG2 gears are switched by controlling solenoids in the transmission with 12v/PWM directly to the solenoids. No CAN in that part. I'll have to control those with my controller myself.

Neutral is achieved by turning off PWM (or applying 0v/50% duty cycle) to both motors. Reverse is achieved by spinning the motors backwards. I'll probably use MG1 alone for reverse.

MG2 gear change will be based on RPM. I have modeled the optimum shift point for maximum performance and will shift MG2 at that point when accelerating. On the way down, it'll shift depending on load.

 

[mira9_cz]

Thank you for reply! There is so many possibilities how to drive two motors most efficiently added by MG2 gears. Splitting the braking power depending on load makes sense. I imagine this will feel nice in the car, sensing the braking force being distributed between the motors.

MG2 gear change will be based on RPM. I have modeled the optimum shift point for maximum performance and will shift MG2 at that point when accelerating.

I understand that MG2 will be commanded to supply power when you need big acceleration. And HI/LOW of MG2 will be shifted automatically by your controller based on MG1 RPM. This RPM point might be smart to not make it fixed, to prevent unnecessary big load to shifting mechanism in case you would pressed the throttle pedal right at the shifting point. I know it is made to handle it, but neither the shifting itself is necessary to be experienced, right?

Sorry for hijacking your thread with my ideas, you made me very excited about those hybrid transmissions and how much possibilities they provide.

 

[bigmouse]

I understand that MG2 will be commanded to supply power when you need big acceleration. And HI/LOW of MG2 will be shifted automatically by your controller based on MG1 RPM. This RPM point might be smart to not make it fixed, to prevent unnecessary big load to shifting mechanism in case you would pressed the throttle pedal right at the shifting point. I know it is made to handle it, but neither the shifting itself is necessary to be experienced, right?

Since the gear shifting will be performed by the same controller that controls the motors, I will be performing the shift in the least jarring and gentlest on the clutches way possible. The flow is this:

Shift is initiated.
MG2 torque command to zero
Clutch opens
MG2 speed after the shift is calculated based on MG1 speed
MG2 speed lowered to the correct speed using speed control loop
Clutch for 2nd gear closes when speed matches
MG2 torque is restored to current throttle setting

This will be felt in the car as a brief "gap" in acceleration, but MG1 can provide some amount of "torque fill" during the shift.

The speed of the shift will depend on how fast the clutches operate and how effectively I can change the speed of MG2.

 

[tylerwatts]

That sounds excellent and should provide a rapid change

 

[mira9_cz]

Since the gear shifting will be performed by the same controller that controls the motors, I will be performing the shift in the least jarring and gentlest on the clutches way possible. The flow is this:

Shift is initiated.
MG2 torque command to zero
Clutch opens
MG2 speed after the shift is calculated based on MG1 speed
MG2 speed lowered to the correct speed using speed control loop
Clutch for 2nd gear closes when speed matches
MG2 torque is restored to current throttle setting

This will be felt in the car as a brief "gap" in acceleration, but MG1 can provide some amount of "torque fill" during the shift.

The speed of the shift will depend on how fast the clutches operate and how effectively I can change the speed of MG2.

Thank you for explanation. It is far better then I could imagine. It really sounds very nice. Good luck and keep us informed about your progress!

 

[joekitch]

using the hybrid transmission from a lexus that has the motor built in? that's legitimately brilliant.....and has a more interesting possibility; parallel hybrid conversions

i'm a complete newbie to this scene but, transmission swaps are not particularly difficult, all things considered.

i have (or, will have) a bmw 540i touring, and this may be a way to make a relatively simple build parallel non-plug-in hybrid setup. you can code a 540i to pretend it has a manual transmission and it'll basically ignore whatever the transmission does in terms of the original transmission control modules....

...if this thing could basically just act as electric assist on acceleration you'd get pretty substantial improvements in city mileage

but does the lexus transmission have its own internal programming for its behavior? would you need some kind of frankenstein transmission control setup where the lexus transmission ECU operates in its own little world oblivious to the rest of the drivetrain?

i'm just super exited about this because it solves a lot of packaging problems with a parallel hybrid build and its essentially off-the-shelf.

 

[bigmouse]

The transmission doesn't have any "programming" in the sense that other automatic transmissions can operate without any ECU input. This one needs to be told what to do by an ECU. That's part of the board that I'm designing for my inverter.

I'd thought about keeping the 3.0L engine that's in my BMW now, as it's a very nice engine. It wouldn't be terribly difficult to mount this transmission to it. But I want a pure EV so I'm not going that route.

 

[joekitch]

The transmission doesn't have any "programming" in the sense that other automatic transmissions can operate without any ECU input. This one needs to be told what to do by an ECU. That's part of the board that I'm designing for my inverter.

I'd thought about keeping the 3.0L engine that's in my BMW now, as it's a very nice engine. It wouldn't be terribly difficult to mount this transmission to it. But I want a pure EV so I'm not going that route.

hmm, so would programming the transmission to act as an "electric assist" like how the old prius did it be feasible? take some strain off the drivetrain during acceleration, it'd seriously increase city mileage

 

[bigmouse]

hmm, so would programming the transmission to act as an "electric assist" like how the old prius did it be feasible? take some strain off the drivetrain during acceleration, it'd seriously increase city mileage

Sounds like you're describing this transmission's intended purpose. This is a hybrid transmission. That's what it was made to do. The difficulty of getting it to do that with a different engine in a different car with a different battery is the only unknown.

 

[joekitch]

Sounds like you're describing this transmission's intended purpose. This is a hybrid transmission. That's what it was made to do. The difficulty of getting it to do that with a different engine in a different car with a different battery is the only unknown.

hmm, could that motor in the transmission also act as the regen braking mechanism during deceleration? or is that better left as a system inside the wheels themselves?

 

[bigmouse]

Okay, something more exciting to show. I got the charger out of a Chevy Volt working so I quickly hooked it up to my inverter as a power supply to try it out. I set it to its lowest setting (200v). The inverter is still running on the breadboard and Arduino with no current sensing but it does have motor position sensing. If you saw my video from back on the 2nd of this running on 12v, 200v will look a bit more impressive. Again, the final voltage will be 650v.

The LEDs that light up are connected to the oil pressure sensors in the transmission. The input shaft isn't locked yet so it spins with the motor and turns the internal pump. Once the input shaft is locked, I'll have to use the electric oil pump. Interesting fact, the transmission defaults to the high speed gear unless I drive the solenoids to get it do downshift to the low speed gear. This is so that if a solenoid or pump fails at high speed, the transmission won't downshift and overspeed the motor.

 

[eldis]

Okay, something more exciting to show. I got the charger out of a Chevy Volt working so I quickly hooked it up to my inverter as a power supply to try it out. I set it to its lowest setting (200v). The inverter is still running on the breadboard and Arduino with no current sensing but it does have motor position sensing. If you saw my video from back on the 2nd of this running on 12v, 200v will look a bit more impressive. Again, the final voltage will be 650v.

Congratulations. I'm also using the Chevy Volt charger for some HV tests - beware that the charger is not a battery, therefore once you start playing with field weakening and regen in general, your motor EMF voltage will exceed your bus voltage (it will try to push current in your charger). As the charger cannot absorb it, one of two things will happen. Either you burn your charger, or the Vbus will go way up high and might damage your inverter.

Good luck!

 

[mira9_cz]

Nice progress, thanks for sharing! You say final voltage will be 650V. I wondered how this work? Motor voltage = battery voltage, so you are going for 650V battery pack? Or there is some step-up from original 288V voltage battery pack to 650V in all cases?

Also I suppose that if you would now hold output shaft by hand, torque would found the way out through gearbox input shaft. Now the torque splits between input and output shaft, so fixing the input shaft is a must. Your output shaft is really rotating at the video only because it has less resistance then the input shaft. Is this correct?

 

[bigmouse]

Nice progress, thanks for sharing! You say final voltage will be 650V. I wondered how this work? Motor voltage = battery voltage, so you are going for 650V battery pack? Or there is some step-up from original 288V voltage battery pack to 650V in all cases?

Also I suppose that if you would now hold output shaft by hand, torque would found the way out through gearbox input shaft. Now the torque splits between input and output shaft, so fixing the input shaft is a must. Your output shaft is really rotating at the video only because it has less resistance then the input shaft. Is this correct?

Hi there. Yes, I'll be using a ~650v battery pack. I have 3 Chevy Volt batteries. I'll be using two of them in series (minus a couple of the small modules to bring the voltage down a bit). The third pack plus the removed modules may end up in a range extending trailer or as stationary storage (or I might sell them).

You are partially correct about the gearing. Only MG1's torque is split between the input and output shafts. In the video, only MG2 is running. If I held the output shaft, the input shaft would not turn because MG2 would not turn. If I was driving MG1 only, then it would work as you describe. In my case, the input shaft IS turning due to friction in the geartrain between the output shaft and MG1. I can hold the input shaft still (like it will be in the car) and MG1 will spin a 2.6x the output shaft speed.

 

[bigmouse]

Congratulations. I'm also using the Chevy Volt charger for some HV tests - beware that the charger is not a battery, therefore once you start playing with field weakening and regen in general, your motor EMF voltage will exceed your bus voltage (it will try to push current in your charger). As the charger cannot absorb it, one of two things will happen. Either you burn your charger, or the Vbus will go way up high and might damage your inverter.

Good luck!

Thanks for pointing that out. You are correct, regen would not be good with a power supply as the only source. The reason I wasn't worried about doing it for this run is because the way I have the code running it's always driving a positive Vq vector. The torque/speed is controlled by changing the magnitude of that vector, so even if I brought the potentiometer all the way to zero quickly, it would just zero out the voltage and never regen. Once I get my control board design done and fabricated, I'll be able to actually use the phase currents for proper FOC. Then I'll switch over to my batteries as a source.

 

[bigmouse]

Bit of a thrill, my project showed up on Hackaday today: http://hackaday.com/2015/05/27/hack...source=feedburner&utm_medium=feed&utm_campaign=Feed:+hackaday/LgoM+(Hack+a+Day)

Also, finished doing the layout for the new inverter control board. Just have to lay out the silk screen designators and I'll be ready to send it off to Seeed to be made. Hopefully things will start moving more quickly once I have a proper PCB made.

Before:

After:

 

[IchibahnSLC]

Bit of a thrill, my project showed up on Hackaday today: http://hackaday.com/2015/05/27/hack...source=feedburner&utm_medium=feed&utm_campaign=Feed:+hackaday/LgoM+(Hack+a+Day)

Also, finished doing the layout for the new inverter control board. Just have to lay out the silk screen designators and I'll be ready to send it off to Seeed to be made. Hopefully things will start moving more quickly once I have a proper PCB made.

Before:

After:

Nice board! I do PCB design sometimes and this image made me itch for some work lol

 

[bigmouse]

Nice board! I do PCB design sometimes and this image made me itch for some work lol

Thanks

PCB design is probably my least favorite thing to do on any of my projects. So tedious. But once I get started and get in the groove I usually enjoy it. It's like solving a puzzle. This one took me 3 solid days of work.

Here's the final version with silk screen.

I'll print it out to scale at work on Monday and verify that the custom footprints I made are actually the right size, then send it off to be made. This version uses a "Teensy 3.1" as the main controller (for ease of programming so I can make quick changes for development), with two smaller ARM microcontrollers to drive each motor. If it works well and I decide to make more, I'll redo the "Teensy" part to be on-board. I'll also change to solderless programming headers at that time. Then the only SMD solder joints will be the connectors.

 

[bigmouse]

Finished populating the new board today. It's sitting on my bench right now with a blinking LED, so that's a good sign! Still got a lot of testing and verification to do, but it's looking good so far. I need to do some programming to really test out the board, so that's where I'm at now.


Pictured below is the new board next to the original Toyota/Lexus board

Here's the new board installed in the inverter. Everything plugs in just like it's supposed to!