# US 2021/0239574 A1 · Method For Dynamic Load Simulation By Means of Parallel Kinematics

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- Number: US 2021/0239574 A1
- Document ID: US20210239574A1
- Status: Published application
- Kind: A1
- Application number: 17/053,743
- Filed: 2019-05-07
- Published: 2021-08-05
- Earliest claimed: 2018-05-07
- Assignees: Universität Paderborn
- Applicants: Universität Paderborn
- Inventors: Ansgar Trächtler; Karl-Peter Jäker; Simon Olma; Andreas Kohlstedt; Phillip Traphöner
- Web page: https://patentgrep.com/patent/US20210239574A1

## CPC

- G01M 7/022: {Vibration control arrangements, e.g. for generating random vibrations}
- G01M 17/04: Suspension or damping
- G05B 17/02: electric
- G05B 2219/23446: HIL hardware in the loop, simulates equipment to which a control module is fixed
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)

## Abstract

The invention relates to a method for dynamic load simulation, wherein loads are specified by target signals and applied to a test object by a parallel kinematic excitation unit via an end effector, including the following operations: measuring loads at a contact point (200), comparing the measured loads with the target signals (300), and determining target pressures (400) for individual actuators of the parallel kinematic excitation unit for applying the target signals by use of a control algorithm (Fq,ref). This provides a method for dynamic load simulation that reduces the time and cost expenditure compared to previously known methods and at the same time enables hardware-in-the-loop simulations to be used.

## Claims

### Claim 1

Method for dynamic load simulation, wherein loads are specified by target signals and applied to a test object by a parallel kinematic excitation unit via an end effector, including the following operations:
measuring loads at a contact point (200);
comparing the measured loads with the target signals (300); and
determining target pressures (400) for individual actuators of the parallel kinematic excitation unit for applying the target signals by use of a control algorithm (Fq,ref).

### Claim 2 (depends on 1)

Method according to claim 1, characterized in that the control algorithm (Fq,ref) comprises at least one variable (ufl,P, τq,ref) to be iterated.

### Claim 3 (depends on 1, 2)

Method according to claim 1 or 2, characterized in that the control algorithm (Fq,ref) includes a compensation for non-linearities.

### Claim 4

Method according to any one of the preceding claims, characterized in that the following control algorithm (Fq,ref) is used:
Fq,ref=JT(z)·[M(z)·z″+C(z, z′)·z′+g(z)+ufl,F],
wherein ufl,F is a new system input for force control, JT(z) is a transposed Jacobian matrix, M(z) is a mass matrix, z is a position vector, C(z, z′)·z′ is a vector of generalized centrifugal and Coriolis forces and g(z) is a vector of generalized weight forces.

### Claim 5

Method according to any one of the preceding claims, characterized in that a new system input (ufl,F) for force control is formed as follows:
ufl,F=τ+RF(τref−τ)+RF,D(τ′ref−τ′),
wherein τ, τ′, τref and τ′ref are load vectors that act between the end effector and the test object and RF and RF,D are control parameters formed as matrices.

### Claim 6

Method according to the preceding claim, characterized in that the control parameters RF and RF,D are determined such that a control error differential equation converges to zero.

### Claim 7 (depends on 1)

Method according to claim 1, characterized in that a direct force control is achieved by the following control algorithm (Fq,ref):
Fq,ref=Fq+JT(z)·[RF(τref−τ)+RF,D(τ′ref−τ′)],
wherein Fq are the forces applied to the end effector by the cylinders of the parallel kinematic excitation unit, JT(z) is a transposed Jacobian matrix, τ, τ′, τref and τ′ref are the load vectors that act between the end effector and the test object, and RF and RF,D are control parameters designed as matrices.

### Claim 8 (depends on 1)

Method according to claim 1, characterized in that the control algorithm (Fq,ref) is selected such that a force or position control can be selected for each degree of freedom, wherein the control algorithm (Fq,ref) is formed as a hybrid force/position control approach.

### Claim 9

Method according to the preceding claim, characterized in that the e n algorithm (Fq,ref) is carried out according to the following equation:
Fq,ref=JT(z)·[C(z, z′)·z′+g(z)+(1−S)·(M(z)·ufl,P+τ)+S·(M(z)·z″+ufl,F],
wherein JT(z) is a transposed Jacobian matrix, C(z, z′)·z′ is a vector of generalized centrifugal and Coriolis forces, z is a position vector, g(z) is a vector of generalized weight forces, S is a selection matrix, M(z) is a mass matrix, τ is a load vector between the end effector and the test object, and ufl,P and ufl,F are the new system inputs for position and force control.

### Claim 10

Method according to any one of the preceding claims, characterized in that a compensation controller, a general transmission element, a PID controller, or a PD controller with an additional sliding mode component is used for force and/or position control.

### Claim 11 (depends on 8, 9, 10)

Method according to any one of claims 8 to 10, characterized in that a means for compensating disturbance variables and/or for adding disturbance variables is used, which is designed such that a disturbance behavior of the control of the target pressures is reduced, wherein disturbance variables to be compensated can be measured or determined directly before the disturbance variables are compensated.

### Claim 12 (depends on 8, 9, 10, 11)

Method according to any one of claims 8 to 11, characterized in that a measured non-linear kinematics and/or dynamics of the test object is determined and used as a precontrol.

### Claim 13

Method according to any one of the preceding claims, characterized in that a phase and/or amplitude drop in a band-limited force control loop is compensated by a phase and amplitude correction.

### Claim 14

Method according to any one of the preceding claims, characterized in that the control algorithm (Fq,ref) is selected such that a model-based compensation of the non-linearities takes place according to the following equation:
Fq,ref=JT(z)·[M(z)·ufl,P+C(z, z′)·z′+g(z)+τ],
wherein JT(z) is a transposed Jacobian matrix, M(z) is a mass matrix, ufl,P is a new system input for force control, z is a position vector, C(z, z′)·z′ is a vector of generalized centrifugal and Coriolis forces, g(z) is a vector of generalized weight forces and τ is a load vector between the end effector and the test object.

### Claim 15

Method according to any one of the preceding claims, characterized in that the control algorithm (Fq,ref) is selected such that the target loads by the actuators are used as the variable (τq,ref) to be iterated:
Fq,ref=JT(z)·τq,ref,
wherein τq,ref are the target loads between the end effecter and the test object and JT(z) is a transposed Jacobian matrix.

### Claim 16

Method according to any one of the preceding claims, characterized in that the parallel kinematic excitation unit is a hexapod.

### Claim 17

Method according to any one of the preceding claims, characterized in that the measuring of loads at the contact point is carried out by a force measuring wheel.

### Claim 18

Method according to any one of the preceding claims, characterized in that the test object is a vehicle axle.

### Claim 19

Method according to any one of the preceding claims, characterized by defining target signals (100) for loads to be applied to the contact point between the end effector and the test object, wherein this is implemented prior to the step of measuring loads at the contact point (200).

### Claim 20

Method according to any one of the preceding claims, characterized by applying the target signals (500) to the end effector by means of a control of the target pressures for the actuators determined by the control algorithm (Fq,ref), wherein this is implemented subsequently to the step of determining the target pressures (400) for individual actuators of the parallel kinematic excitation unit.

### Claim 21

System for dynamic load simulation between a parallel kinematic excitation unit and a test object, comprising components suitable for carrying out method steps according to at least one of the preceding claims.