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CONTROL
In the first instance, the control of the electric drive adjusts the
speed and torque of the electric motor. The control system has
to be chosen and developed with regard to the design of the
drive, the machine type and corresponding power electronics.
Usually this control system uses cascade structures to perform
different tasks, like current control or speed control. The
performance of modern digital signal processors and their
intelligent programming allows them to be employed as a
multitasking operating system to implement sophisticated
control structures.
Besides time-critical tasks (such as controlling the semiconductor
valves for the power electronics), the control parameters of the
electric drive can be monitored and adapted continuously. In this
way the influences of temperature or different loads on the
drivetrain can be compensated. By adapting the control
parameters, the entire drive can be operated at a predefined
optimum.
Additional tasks which the signal processor can perform using
appropriate algorithms include: diagnosing the status of the
electric machine, sensorless control of the machine, and
handling communications between the electric drive and the
vehicle’s energy management system. The basis for
programming the signal processor is the mathematical modelling
of the drivetrain components. Appropriate simulation tools
support this development and optimisation process, reducing
the expenditure required to implement the mathematical models
as executable codes. Sophisticated modelling of the drivetrain
components is therefore required to realise real-time enabled
models with an appropriate level of detail.
ELECTRIC DRIVES
Besides considering and optimising these electric drive
components, attention also needs to be given to how the entire
electric drive (comprising the electrical energy storage, the
power electronics, and the electric motor) is interconnected. The
cabling of the components has to be kept as short as possible
to prevent additional losses. Development efforts therefore
need to focus on strong integration of the electric machine and
the power electronics.
In addition, high-voltage concepts are needed to provide the
power for electric propulsion without high losses and weight.
Using high voltage consequently raises safety issues and
requires appropriate safety concepts, supported by highly
integrated electric drivetrain components.
Summarizing the key issues of electric drive development for
automotive applications, includes consideration of the electric
components within the context of the given vehicle concept, the
optimisation of the components within with the given system
and the use of the latest materials, technologies and
development tools.
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