Electric Marine Propulsion Throttle Filtering for Smooth Deceleration
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Solution Overview
Problem
Electric marine propulsion systems face risks of sudden and dangerous deceleration when an operator rapidly shifts from high to low throttle due to the instantaneous ability of electric motors to stop rotation, posing a threat to the vessel and its occupants.
Innovation Solution
Implementing a control system that filters operator demand signals to gradually reduce motor input when a rapid throttle change is detected, ensuring safe and controlled vessel deceleration by applying a filter latch condition and unlatching condition based on predefined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric motor responds instantaneously to operator throttle commands, then the system responsiveness and acceleration performance are improved, but sudden and dangerous deceleration occurs when operator rapidly shifts from high to low throttle
Solution Approach 1:
A filter latch condition is introduced as an intermediary mechanism between the operator's throttle command and the motor controller. When a rapid throttle reduction is detected, the filter latch condition is satisfied, causing the controller to latch the filtered throttle position and prevent instantaneous motor shutdown. This intermediary filter mechanism mediates between the operator's intent and the motor's response, eliminating harmful sudden deceleration while preserving normal responsive operation.
Solution Approach 2:
The control system performs preliminary detection of rapid throttle changes by monitoring the throttle position rate of change. Before the motor controller executes the throttle command, the system pre-emptively identifies panic shift conditions and applies filtering. This preliminary action prevents the harmful effect from occurring in the first place, rather than reacting after deceleration has already begun.
2Reliability
If a filter is applied to throttle commands to prevent sudden deceleration, then safety is improved, but the system response time increases and acceleration performance deteriorates
Solution Approach 1:
The filtering mechanism is made dynamic rather than static. The filter latch condition is satisfied only when specific criteria are met (rapid throttle reduction detected), allowing normal fast response under normal operating conditions. When the filter latch condition is satisfied, the system transitions to a latched state that prevents harmful deceleration. The filter dynamically adapts its behavior based on operating conditions, applying restraint only when necessary while maintaining responsiveness otherwise.
Solution Approach 2:
The control system changes the effective time constant parameter of the throttle response based on operating conditions. Under normal conditions, the response time constant is short for fast response. When a panic shift condition is detected, the system effectively increases the time constant by latching the filtered throttle position, thereby reducing the response speed to prevent dangerous deceleration. This parameter change allows the system to optimize between speed and safety based on context.
3Reliability
If the control system continuously monitors throttle position rate of change to detect filter latch conditions, then safety monitoring capability is improved, but device complexity increases
Solution Approach 1:
The throttle position rate of change monitoring serves multiple functions: it is used to detect filter latch conditions for safety, to determine when to apply filtering, and to monitor system state for control decisions. By making this single monitoring mechanism multi-functional, the system achieves enhanced safety monitoring capability without proportionally increasing complexity. The same monitoring infrastructure supports both safety detection and normal control operations.
Data Source
AI summary
An electric marine propulsion system for a marine vessel is provided. The system includes a power storage system, an electric motor powered by the power storage system and configured to rotate a propulsor to propel the marine vessel, and a control system. The control system is configured to operate the electric motor according to an operator demand signal, determine whether at least one filter latch condition is satisfied, and responsive to a determination that the at least one filter latch condition is satisfied, operate the electric motor according to a filtered motor input.