Food Processor Motor Speed Control Using PWM and Field Weakening
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing food processing machines with brushless DC motors are limited in maximum speed during no-load or light-load states, necessitating a method to increase rotational speed effectively.
Innovation Solution
A food processing machine with a rotational speed increasing control method that generates a PWM control signal with a gradually increasing duty ratio and performs field weakening control, utilizing a Hall advance angle to enhance motor speed, along with a stator iron core and rotor iron core design optimizing magnetic flux distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a brushless DC motor is used in the food processing machine, then the motor achieves forward and reverse rotation with low noise and no carbon powder, but the maximum speed in no-load or light-load state is limited
Solution Approach 1:
The patent applies parameter changes by modifying the PWM duty cycle from a fixed value to a dynamically adjustable parameter. The controller increases the PWM duty cycle in a step-by-step manner during no-load or light-load operations, thereby increasing the average voltage applied to the motor and enabling the motor to achieve higher rotational speeds beyond the original limitation while maintaining reliable operation.
2Speed
If the PWM duty cycle is increased to raise motor speed, then the average current delivered to the motor increases, but the motor still cannot exceed its maximum speed threshold without field weakening
Solution Approach 1:
The patent applies dynamics by making the PWM duty cycle dynamic rather than static. The controller continuously adjusts the duty cycle based on the motor's operating conditions, increasing it in controlled steps during no-load or light-load states to maximize speed while managing power consumption efficiently. This dynamic adjustment allows the system to optimize the balance between speed and power usage in real-time.
3Speed
If field weakening control is applied to rapidly increase rotational speed, then the maximum speed threshold is exceeded, but the control complexity increases
Solution Approach 1:
The patent applies feedback by implementing a closed-loop control system that monitors the motor's operational state and adjusts the PWM duty cycle accordingly. The controller detects no-load or light-load conditions and responds by progressively increasing the duty cycle, while also incorporating field weakening control when the speed threshold is approached. This feedback mechanism manages the complexity by automating the control decisions based on real-time motor performance data.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows the brushless DC motor to reach high rotational speeds within its maximum threshold, improving efficiency and performance during no-load or light-load conditions.
Implementation Method 1
a brushless DC motor... The motor is driven by a periodic drive signal (PWM)... The drive signal has a constant frequency and amplitude, but a variable duty cycle
Implementation Method 2
performing a field weakening control on the driving motor to rapidly increase the rotational speed of the driving motor
Implementation Method 3
generating a pulse width modulation (PWM) control signal according to the target rotational speed to control the driving motor... gradually increasing a duty ratio of the PWM control signal
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A food processor (200) and a rotational speed increase control method and apparatus therefor. The rotary speed increase control method comprises the following steps: when the food processor (200) is idle or in a light load state, obtain a rotational speed instruction (SI); analyze the rotational speed instruction to acquire a target rotational speed for a drive motor (100), and generate a PWM control signal according to the target rotational speed so as to control the drive motor (100) (S2); during the process of controlling the drive motor (100), gradually increase the duty cycle of the PWM control signal according to a progressive increment mode until the duty cycle of the PWM control signal reaches 1; and carry out weak magnetic control on the drive motor (100) so as to quickly increase the rotational speed of the drive motor (100) (S3); thus, the rotational speed of the drive motor (100) may be very high within a maximum threshold range allowed by the drive motor (100).