Technology "not being good enough yet" does not prevent you from standardizing the inputs/outputs so that companies can still improve their individual implementation of the black box. A motor-drive unit has basically only four essential inputs: DC power, drive and regen power limits depending on battery condition and set-point for RPM or torque up to whatever the power limit will allow or design limits, whichever comes first, while non-mechanical outputs are just telemetry to monitor its state. You don't need to discover the most efficient electric motor design theoretically possible and technically feasible to decide on a standard interface for that. Same goes for coolant pumps and routing valves, you don't need to decide on the best pump and valve design ever before cooking up a standard for how to power and control them regardless of the physical implementation.
I agree on the greater premise. But when GM decides to put an O2 sensor in its newest engine design the O2 sensor design is so standardized that completely reinventing the wheel and building their own new O2 sensor is counter productive. So in most cases while the sensor may have some packaging differences to make it a "GM" sensor it is at its core the same sensor that Ford is using in its vehicles, probably produced in the same factory by the same OEM outsource manufacturer. While at its core the O2 sensor is considered off the shelf today that wasn't always the case. It is an ICE specific design that took quite a while to develop as a standard part and because of its limited application outside autos (sensing oxygen levels in a stream of very hot exhaust gas) it is pretty much useless for anything else.
"Off the shelf" for electric power trains really comes from the industrial side. Most of those designs are hardwired. So while I could technically go to an industrial supply house right now and purchase a battery bank, dc drive, dc motor, and mechanical transmission they would not work well for the application of slapping them in in the place of an ICE powertrain. Even if I developed a car around the powertrain I certainly wouldn't get anything near what tesla or GM is getting from their designs. That has lead to very proprietary systems being developed to make the powertrains efficient for the auto application. Things like water cooled mesh wound DC electric motors (while they do exist in very niche markets) are almost unheard of in industrial controls. But put a few million autos on the street and it becomes an off the shelf part. Most of the solid state industrial motor control tech is catered to an AC input outputted to a 3 phase AC motor. These designs, while critical for the industrial applications they are used for, are useless for the auto industry. DC motors (in the power range that autos use) are pretty non existent in the industrial scene as well. The electric car market is not volume developed enough bring the OEM manufactures and until they develop standardized components "off the shelf" electric car components don't exist yet.
To your "A motor-drive unit has basically only four essential inputs" comment. You have completely lost me there. The only power input is from the battery bank. You have some control parameters listed in there (limits, RPM set point) and torque. These things are all controlled by the drive, which even in a dc system is going to be a PWM design. Regenerative braking isn't really an input at all, but a byproduct to be dealt with when you use your drive motor to reduce speed (temporally making it a generator rather than a motor). Diesel electric trains and many industrial speed controller designs have to employ braking resistors to bleed off the excess dc bus voltage in the form of heat for decades. Elegant designs store as much of this energy as possible to be fed back into the system for reuse but at best it is a glorified battery charger that cannot operate at the same time that output power demand is active.
The torque band on an electric motor is pretty much flat which is why it kills ICE on a drag strip. Ultra low rpm and ultra high rpm falls off, but everything in the middle is even. So torque limits are either a max system limit (current limited), or a waveform modification to control "slip" in the motor by artificially strengthening/weakening the flux field (which can greatly improve efficiency). RPM is mostly controlled by pulse frequency leveled by motor inductance from the PWM (minus mechanical slip). Because of the slippage issue the most expensive drives involve an encoder feedback system coupled with input/output power bus monitoring on the drive to accurately model the internal flux field characteristics of the motor and adjust accordingly. Cheap drives, golf carts and power wheels simply use a voltage control model that again doesn't work well in the auto application. The efficiency gains are pretty big with the more advanced designs but there are so many tweaks that can be done in an auto application that it again lends to proprietary drive designs having a significant advantage. This is a big reason that EZGO isn't the premier electric car producer in the world today, but they make a good golf cart.
This doesn't even go into the battery bank challenges.
When all auto players are really at ramped production the industry will self standardize to minimize costs. Tesla, if it can survive, is probably the exception due to their vertical supply chain mindset. Even so I would not expect to be able to easily put a GM component into a Ford or vice versa. Then again try sticking a ICE GM V8 ECM on a Ford V8 today and see what happens.
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