Simulation of a system a mechanical subsystem and a hydraulic subsystem
First Claim
1. A method (90) for simulating a system having a mechanical subsystem and a hydraulic subsystem, said mechanical subsystem having a number of bodies and said hydraulic subsystem having a number of hydraulic actuators with hydraulic cylinders, said number of bodies being at least one and said number of hydraulic actuators being at least one, characterized in that the mechanical subsystem and the effect of the hydraulic subsystem thereupon is described by a first differential equation system of an n-dimensional first variable, the first variable comprising coordinates defining the configuration of said mechanical subsystem and the effect of the hydraulic subsystem on the mechanical subsystem being taken into account using actuator forces, the hydraulic subsystem and the effect of the mechanical subsystem thereupon is described by a second differential equation system of an nm-dimensional second variable, the second variable relating to pressures in said hydraulic cylinders, the first differential equation system is discretized using a first numerical integration method, the second differential equation system is discretized using a second numerical integration method, and in that for each time step of the simulation, after an initialization step, the method comprises the following steps, performed by means of a computer:
- determining a current value for the second variable using the discretization of the second differential equation system, a previous value for the first variable and a previous value for the second variable, said previous values having been determined in a previous time step, computing current actuator forces using at least the current value of the second variable, and determining a current value for the first variable using the discretization of the first differential equation system, the current actuator forces and the previous value for the first variable.
1 Assignment
0 Petitions
Accused Products
Abstract
A method (90) for simulating a system having a mechanical subsystem and a hydraulic subsystem is presented. The method comprises the steps of: describing (92) the mechanical subsystem and the effect of the hydraulic subsystem thereupon by integrating a first differential equation system of an n-dimensional first variable using a first numerical method, resulting in a sequence of values for the first variable; and describing (94) the hydraulic subsystem and the effect of the mechanical subsystem thereupon by integrating a second differential equation system of an m-dimensional second variable using a second numerical method, resulting in a sequence of values for the second variable. A corresponding arrangement having a first integrator (1) and a second integrator (4) is also presented.
11 Citations
34 Claims
-
1. A method (90) for simulating a system having a mechanical subsystem and a hydraulic subsystem, said mechanical subsystem having a number of bodies and said hydraulic subsystem having a number of hydraulic actuators with hydraulic cylinders, said number of bodies being at least one and said number of hydraulic actuators being at least one, characterized in that
the mechanical subsystem and the effect of the hydraulic subsystem thereupon is described by a first differential equation system of an n-dimensional first variable, the first variable comprising coordinates defining the configuration of said mechanical subsystem and the effect of the hydraulic subsystem on the mechanical subsystem being taken into account using actuator forces, the hydraulic subsystem and the effect of the mechanical subsystem thereupon is described by a second differential equation system of an nm-dimensional second variable, the second variable relating to pressures in said hydraulic cylinders, the first differential equation system is discretized using a first numerical integration method, the second differential equation system is discretized using a second numerical integration method, and in that for each time step of the simulation, after an initialization step, the method comprises the following steps, performed by means of a computer: -
determining a current value for the second variable using the discretization of the second differential equation system, a previous value for the first variable and a previous value for the second variable, said previous values having been determined in a previous time step, computing current actuator forces using at least the current value of the second variable, and determining a current value for the first variable using the discretization of the first differential equation system, the current actuator forces and the previous value for the first variable. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
-
-
25. A computer program for simulating a system having a mechanical subsystem and a hydraulic subsystem, said mechanical subsystem having a number of bodies and said hydraulic subsystem having a number of hydraulic actuators with hydraulic cylinders, said number of bodies being at least one and said number of hydraulic actuators being at least one, characterized in that said computer program comprises computer program code means adapted to perform, for each time step of the simulation after an initialization step, the following steps when the program is run on a computer:
-
determining a current value for a second variable using a discretization of a second differential equation system, a previous value for the second variable and a previous value for a first variable, where the second differential equation system of the m-dimensional second variable, which relates to pressures in said hydraulic cylinders, describes the hydraulic subsystem and the effect of the mechanical subsystem thereupon, the second differential equation system is being discretized using a second numerical integration method and said previous values of the first and second variables have been determined in a previous time step, computing current actuator forces using at least the current value of the second variable, and determining a current value for the first variable using a discretization of a first differential equation system, the current actuator forces and the previous value for the first variable, where the first differential equation system of the n-dimensional first variable, which comprises coordinates defining the configuration of said mechanical subsystem, describes the mechanical subsystem and the effect of the hydraulic subsystem thereupon, the effect of the hydraulic subsystem on the mechanical subsystem is being taken into account using the actuator forces, and the first differential equation system is being discretized using a first numerical integration method. - View Dependent Claims (26)
-
-
27. A simulation arrangement for simulating a system having a mechanical subsystem and a hydraulic subsystem, said mechanical subsystem having a number of bodies and said hydraulic subsystem having a number of hydraulic actuators with hydraulic cylinders, said number of bodies being at least one and said number of hydraulic actuators being at least one, characterized in that it comprises
means (4) for determining a current value for a second variable using a discretization of a second differential equation system, a previous value for the second variable and a previous value for a first variable, where the second differential equation system of the nm-dimensional second variable, which relates to pressures in said hydraulic cylinders, describes the hydraulic subsystem and the effect of the mechanical subsystem thereupon, the second differential equation system is being discretized using a second numerical integration method and said previous values of the first and second variables have been determined in a previous time step, means for computing current actuator forces using at least the current value of the second variable, and means (1, 3) for determining a current value for the first variable using a discretization of a first differential equation system, the current actuator forces and the previous value for the first variable, where the first differential equation system of the n-dimensional first variable, which comprises coordinates defining the configuration of said mechanical subsystem, describes the mechanical subsystem and the effect of the hydraulic subsystem thereupon, the effect of the hydraulic subsystem on the mechanical subsystem is being taken into account using actuator forces, and the first differential equation system is being discretized using a first numerical integration method, and in that said means for determining the current value for the second variable, said means for computing the current actuator forces the and said means for determining the current value for the first variable are adapted to be active for each time step of the simulation after an initialization step.
Specification