Laundry Load Inertia Estimation via Dual-Frequency Dither Signals
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Solution Overview
Problem
Existing methods for estimating load behavior in laundry treatment machines are not easy, reliable, or accurate, particularly in large drums with varying load inertia, leading to potential mechanical impacts between the tub and cabinet during resonance.
Innovation Solution
A method involving two operations with different speed controller parameters and bandwidths to determine load inertia and torque using equations (1) and (2), and a load torque observer that estimates load torque without additional hardware, allowing estimation at a constant angular speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an acceleration ramp is used to estimate load inertia, then the estimation can be performed, but it increases the risk of mechanical impact between the tub and cabinet during resonance
Solution Approach 1:
The patent applies periodic action by using sinusoidal dither signals at two different frequencies (first and second frequencies) to excite the mechanical system. This periodic excitation allows estimation of load inertia through the response to these periodic inputs, avoiding the need for acceleration ramps that cause mechanical impacts during resonance.
Solution Approach 2:
The patent utilizes mechanical vibration by introducing controlled vibrations through dither signals at specific frequencies. The system measures the response to these vibrations to determine load inertia, thereby avoiding mechanical impacts while achieving accurate estimation through vibrational analysis.
2Quantity of substance
If the drum size and loading capacity are increased, then the laundry treatment machine can handle more laundry, but the space between the tub and cabinet decreases making precise estimation more critical
Solution Approach 1:
The patent introduces an intermediary approach by using dither signals as a mediating input to probe the system's response. This allows indirect measurement of load unbalance and inertia through the system's reaction to controlled excitations, enabling precise estimation even in large drums with reduced clearance.
Solution Approach 2:
The patent applies parameter changes by varying the frequency parameters of the dither signals (using two different frequencies) to extract information about load inertia and unbalance. This parametric approach enables precise measurement without requiring physical changes to the drum-cabinet spacing.
3Measurement precision
If additional hardware sensors are added to improve estimation accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent applies self-service by using the existing control unit and available sensors (encoder, current sensors) to perform load torque estimation. The control unit itself generates the dither signals and processes the response, making the system self-sufficient without requiring additional dedicated hardware sensors for measurement.
Solution Approach 2:
The patent demonstrates universality by making the control unit perform multiple functions: generating dither signals, measuring system response, calculating load torque, and controlling the motor. This multi-functional approach eliminates the need for separate dedicated hardware components for each function.
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
Enables precise estimation of load inertia and torque, avoiding mechanical impacts and optimizing resource use by estimating dry or wet loads without acceleration ramps, applicable to large drums and existing control units.
Implementation Method 1
The speed controller regulates the angular speed of the drive motor and is part of the speed control loop
Implementation Method 2
The drive motor rotates the drum around a horizontal rotational axis
Implementation Method 3
The washing unit is suspended to the cabinet by a set of springs and dampers
Implementation Method 4
The washing unit is suspended to the cabinet by a set of springs and dampers
Implementation Method 5
The load torque observer enables an accurate and continuous estimation of the load torque
Data Source
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AI summary
A method to estimate a load behavior in a laundry treatment machine comprises the step of determining an inertia (Ĵt, ĴL) and/or a load torque caused by a load depending on a first torque signal Tem*1, a second torque signal Tem*2, a derivative ω˙1^ of a first angular speed signal and a derivative ω˙2^ of a second angular speed signal. These signals are based on a first operation and a second operation of the laundry treatment machine, wherein a controller of the laundry treatment machine is operated with different controller parameters (P1, P2). The method enables to estimate the load behavior in an easy, reliable and accurate manner.