Multi-Body Standstill Control Using Velocity Dead Zone Filtering
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Solution Overview
Problem
Existing velocity control methods for multi-body systems face stability issues at standstill due to static friction, where measurement noise leads to continuous control errors and potential loss of stability, as the controller is designed based on incorrect models of inertia and mass, especially when static friction is not accurately predicted.
Innovation Solution
A dead zone element is introduced in the velocity control loop to handle measurement noise by converting measurement velocities to dead zone velocities, which are used as actual velocities for control, disconnecting the control loop at standstill to prevent destabilization, and parameterized to suppress measurement noise effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a velocity controller is designed based on accurate models of inertia and mass, then control precision is improved, but device complexity increases and accurate prediction of static friction becomes difficult
Solution Approach 1:
The patent changes the control parameter from velocity to acceleration by introducing a differentiator between the velocity controller and actuator. This parameter transformation simplifies the control model by eliminating the need for accurate inertia and mass predictions, as the acceleration controller directly responds to velocity errors without requiring complex dynamic models of the multi-body system.
2Reliability
If measurement noise is suppressed by filtering, then control stability is improved, but response speed decreases
Solution Approach 1:
The patent transforms the control signal from velocity to acceleration, which inherently filters out low-frequency measurement noise while preserving high-frequency dynamic responses. The differentiator operation naturally attenuates noise components without requiring additional filtering stages that would slow down the system response.
Solution Approach 2:
The patent replaces mechanical filtering (physical damping elements) with a mathematical differentiator in the control algorithm. This substitution achieves noise suppression through signal processing rather than mechanical means, maintaining fast response characteristics while improving control stability.
3Reliability
If static friction is accurately predicted and compensated, then standstill stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the control approach from velocity-based to acceleration-based control. This parameter transformation eliminates the need for static friction compensation because the acceleration controller naturally adapts to friction forces by adjusting the control output based on actual velocity deviations, without requiring precise friction models or high-precision mechanical components.
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 approach ensures stable operation of multi-body systems at standstill without requiring accurate models, suppressing measurement noise and preventing oscillations and limit cycles, thus maintaining control loop stability and reducing mechanical stress.
Implementation Method 1
A dead zone element is introduced in the velocity control loop to handle measurement noise by converting measurement velocities to dead zone velocities
Implementation Method 2
a velocity controller determines, from a specified target velocity vtarget=0 and from an actual velocity of the multi-body system, a control variable for adjusting the actual velocity to the target velocity
Implementation Method 3
the control variable is converted by an actuator into a drive force acting on the drive body
Implementation Method 4
wherein a static friction acts on the friction body
Data Source
AI summary
A method for standstill control of a multi-body system (MKS) having at least one drive body and at least one friction body mechanically coupled to the drive body. A static friction acts on the friction body, a velocity of one of the bodies of the MKS is determined as measurement velocity subject to a measurement noise and converted in a dead zone element to a dead zone velocity. The dead zone velocity assumes the value of zero for values of the measurement velocity above a value of zero and below a positive dead zone limit, and assumes the value of the measurement velocity for values of the measurement velocity above the positive dead zone limit. The dead zone velocity is provided to a velocity controller as an actual velocity for controlling.