Motor Control Apparatus Dynamic Offset Temperature Estimation
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Solution Overview
Problem
Conventional motor control apparatuses face challenges in accurately estimating motor component temperatures due to factors like changes in supply voltage, duty cycles, and heat generation differences between phases, leading to excessive current limitations and reduced motor performance.
Innovation Solution
A motor control apparatus that includes a primary delay arithmetic unit, sensor value adder, offset adder, response constant determination portion, and offset temperature determination portion, which adjust the gain, time constant, and offset temperature based on supply voltage and heat generation changes to improve temperature estimation precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed offset temperature is used for temperature estimation, then the estimation is simple to implement, but the current is excessively limited when supply voltage is low, reducing motor performance
Solution Approach 1:
The offset temperature is changed dynamically based on the supply voltage level. When supply voltage is high, a larger offset temperature is applied; when supply voltage is low, a smaller offset temperature is applied. This dynamic adjustment prevents excessive current limitation while maintaining adequate temperature estimation, thereby improving motor performance without sacrificing implementation simplicity.
Solution Approach 2:
The offset temperature parameter is adjusted according to the supply voltage parameter. By changing the offset temperature value based on voltage conditions, the system adapts to different operating states, avoiding unnecessary current limitation and enabling the motor to operate at full performance when voltage is low.
2Device complexity
If fixed gain and time constant are used in primary delay response, then the calculation is simple, but temperature estimation precision is insufficient when duty changes, leading to excessive current limitation
Solution Approach 1:
The gain and time constant parameters of the primary delay response are changed dynamically based on the duty cycle. When duty is high, different gain and time constant values are used compared to when duty is low. This dynamic parameter adjustment maintains accurate temperature estimation across varying duty conditions without requiring complex calculation structures.
Solution Approach 2:
The system changes the parameters (gain and time constant) of the primary delay response according to the duty cycle. By adapting these parameters to the current operating condition, the system achieves precise temperature estimation while keeping the calculation approach relatively simple through parameter lookup tables or predefined relationships.
3Stability of the object's composition
If uniform heat generation correction is applied to all components, then the temperature estimation is consistent, but the current is excessively limited due to unaccounted self-heat generation and heat from other components
Solution Approach 1:
Instead of applying uniform heat generation correction to all components, the system applies differentiated correction based on the specific component being estimated (e.g., switching elements vs. motor coil). Each component type receives appropriate heat generation accounting, including self-heat generation and heat from other components, leading to more accurate local temperature estimates and reduced excessive current limitation.
Data Source
AI summary
A motor control apparatus that estimates a temperature of a temperature estimation target element at a time of energizing the motor and drives a motor by controlling an electric power is provided. The motor control apparatus includes a primary delay arithmetic unit that outputs a primary delay response as an amount of temperature change, a sensor value adder that adds a sensor value of a temperature sensor to the amount of temperature change, an offset adder that adds an offset temperature to an output of the sensor value adder, a response constant determination portion that determines the gain and the time constant, and an offset temperature determination portion. At least one of the response constant and the offset temperature is changed according to a supply voltage or an input voltage.