What is adaptive acceleration control?

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November 2020 Motion Control & Drives

Adaptive acceleration control (AAC) is a new soft start control type that allows the selection of different acceleration and deceleration profiles according to application needs. Soft starters offer a variety of methods for the control of motor starting and stopping. Each type of the control uses a different primary control parameter.

Constant current is the traditional form of soft starting, which raises the current from zero to a specified level and keeps the current stable at that level until the motor has accelerated. Constant current starting is ideal for applications where the start current must be kept below a particular level.

Current ramp soft starting raises the current from a specified starting level to a maximum limit over an extended period of time. Current ramp starting can be useful for applications where the load varies between starts, the load breaks away easily but starting time needs to be extended, or the electricity supply is limited.

Kickstart provides a short boost of extra torque at the beginning of a start, and can be used in conjunction with current ramp or constant current starting. Kickstart can be useful to help start loads that require high breakaway torque but then accelerate easily (for example flywheel loads such as presses).

AAC is a new intelligent motor control technique. In an AAC soft start, the ASAB soft starter adjusts the current in order to start the motor within a specified time and using a selected acceleration profile. It is based on two algorithms, one for measuring (learning) the motor characteristics and one for controlling the motor. During each start it makes two speed estimates, zero speed at LR and maximum speed at the point when the motor is operating at maximum efficiency. During subsequent start and stop operations, measuring the motor characteristics and using this value to determine the speed between the two known end points provides an estimate of motor speed. The control algorithm creates a time based speed profile which can create curves from a mathematical function. During each start and stop operation the control algorithm compares the speed estimate with the speed ramp profile. If the speed estimate is too low it increases the power to the motor and decreases the power when it is too high. This allows for control of the three accelerating and three decelerating profiles, and if the motor does not start and stop smoothly to fine-tune adjust the adaptive control gain.

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Motion Control & Drives

What is adaptive acceleration control?

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