Vehicle Mirror Housing Rotation With PWM Speed Control
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Solution Overview
Problem
Existing motor-driven viewing devices for vehicles require multiple motors for adjusting mirror or camera orientation, leading to complexity and inefficiency in both automatic and user-controlled settings, especially under varying environmental conditions.
Innovation Solution
A motor-driven viewing device that uses a single DC motor for both folding and user-controlled rotation, employing pulse width modulation to achieve different rotation speeds, and an additional motor for transverse rotation, with a feedback loop to adjust current duty cycles based on rotation speed sensors, ensuring efficient operation across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single DC motor is used for both folding and user-controlled rotation, then the number of motors is reduced, but the rotation speed control becomes more complex
Solution Approach 1:
The patent applies pulse width modulation (PWM) to control the DC motor, using periodic electrical pulses with varying duty cycles to achieve different rotation speeds. This allows a single motor to perform multiple functions (folding and user-controlled rotation) by modulating the electrical input rather than using separate motors for each function.
Solution Approach 2:
The single DC motor is designed to perform multiple functions: driving the housing from folded to operational position and enabling user-controlled mirror/camera orientation adjustment. This multi-functionality reduces the overall number of motors required in the system while maintaining full operational capability.
2Productivity
If high rotation speed is used for folding, then the folding time is reduced, but the user control becomes impracticable
Solution Approach 1:
Pulse width modulation is used to vary the duty cycle of electrical pulses supplied to the motor, enabling different effective rotation speeds. During folding operations, higher duty cycles provide fast movement, while during user-controlled adjustment, lower duty cycles provide manageable rotation speeds for precise positioning.
Solution Approach 2:
The motor rotation speed is made dynamic and adjustable rather than fixed. The system can adapt the rotation speed based on the operational phase: fast speed for folding/unfolding operations and controlled slower speed for user-adjustment operations, optimizing both productivity and ease of operation.
3Speed
If pulse width modulation is used to control rotation speed, then different speeds are achieved, but energy consumption varies
Solution Approach 1:
Pulse width modulation controls motor energy consumption by varying the duty cycle of electrical pulses. During fast folding operations, higher duty cycles deliver more energy for rapid movement. During user-controlled adjustment, lower duty cycles reduce energy consumption while providing sufficient controlled rotation speed.
Solution Approach 2:
The electrical parameters (voltage, current, duty cycle) supplied to the motor are dynamically changed based on operational requirements. This allows optimization of energy consumption by matching the energy input to the actual mechanical work required at different operational phases.
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
This solution reduces the number of motors needed, enhances user control by maintaining practical adjustment speeds, and ensures reliable operation under voltage, wind, and temperature variations, while minimizing overshoot and energy consumption.
Implementation Method 1
The same electric DC motor is used both to drive rotation of the housing from its folded position to its operating position and to drive user controlled rotation around the first rotation axis
Implementation Method 2
Pulse width modulation is used to modulate the current to the electric motor so that different angular rotation speeds of the mirror or camera are realized during rotation of the housing from its folded position to its operating position and during user controlled rotation
Implementation Method 3
a feedback loop to adjust current duty cycles based on rotation speed sensors, ensuring efficient operation across varying conditions
Data Source
Figure 1~2
Figure 3~3a
AI summary
The vehicle mounted backward viewing device has a base structure for mounting the viewing device on the vehicle, a rotatable housing and a mirror or camera in the housing. An electric DC motor drives a rotation of the housing relative to the base structure. A control circuit having provides for user control of orientation of the mirror or camera by rotating the housing. The control circuit comprises a pulse width modulation circuit. When the motor driven viewing device is powered on, the housing to be rotated from a folded orientation to an operational orientation by causing the pulse width modulation circuit to supply current from the power supply input to the electric DC motor using a first supply current duty cycle level, of preferably 100%. When the housing is rotated to adjust the orientation, the control circuit causes the pulse width modulation circuit to supply the current using a second supply current duty cycle level, lower than the first supply current duty cycle level.