Method of operating an active suspension

1. A method of operating an active suspension of a motor vehicle, said method comprising:

adding power to at least one active control element of the active suspension, arranged between a wheel and a body, for damping a movement of the motor vehicle in a vertical direction when negotiating a terrain to thereby influence a control variable of the suspension, wherein the control variable of the active suspension is a path traveled in the vertical direction or the control variable of the active suspension is a force acting in the vertical direction;

determining a first signal of a velocity of the body in the vertical direction and a second signal of the control variable;

determining a value for a mechanical energy derived from the second signal;

comparing the mechanical energy with a predefined threshold value for the mechanical energy;

determining a phase shift between the first and second signals;

comparing a value of the phase shift with a predefined threshold value;

identifying a presence of excitation of the vertical body movement when the value of the phase shift deviates from the predefined threshold value at least by a tolerance value or when the value of the phase shift is greater than the predefined threshold value so that an excitation index has the value one.

2. The method of claim 1 , further comprising measuring an acceleration of the body in the vertical direction, and calculating the velocity of the body in the vertical direction through integration.

3. The method of claim 1 , further comprising determining the mechanical energy resulting from the control variable in the vertical direction, wherein the excitation of the movement is identified in the vertical direction, when the value of the determined mechanical energy deviates from the predefined threshold value for the mechanical energy at least by a tolerance value for the mechanical energy.

4. The method of claim 1 , further comprising connecting the body according to the Skyhook principle via a virtual damper with a reference system.

5. The method of claim 1 , further comprising initiating a counter measure, when identifying the presence of excitation of the movement in the vertical direction.

6. The method of claim 1 , further comprising filtering each of the first and second signals by a high-pass filter and a low-pass filter, said high-pass filter and low-pass filter having a cut-off at 1 Hz.

7. A method of operating a plurality of active suspensions of a motor vehicle, with the active suspensions being arranged respectively between a wheel of plural wheels and a body of the motor vehicle, said method comprising:

adding power to at least one active control element of each of the active suspension for damping a movement of the motor vehicle in a vertical direction when negotiating a terrain to thereby influence a control variable of the suspension, wherein the control variable of the active suspension is a path traveled in the vertical direction or the control variable of the active suspension is a force acting in the vertical direction;

determining a first signal of a velocity of the body in the vertical direction and a second signal of the control variable;

determining a value for a mechanical energy derived from the second signal;

comparing the mechanical energy with a predefined threshold value for the mechanical energy,

determining a phase shift between the first and second signals;

comparing a value of the phase shift with a predefined threshold value;

identifying a presence of excitation of the vertical body movement when the value of the phase shift deviates from the predefined threshold value at least by a tolerance value or when the value of the phase shift is greater than the predefined threshold value so that an excitation index has the value one.

8. The method of claim 7 , further comprising filtering each of the first and second signals by a high-pass filter and a low-pass filter, said high-pass filter and low-pass filter having a cut-off at 1 Hz.

9. An operating system for a motor vehicle, comprising:

an active suspension arranged between a wheel and a body of the motor vehicle and having at least one active control element configured to damp a movement of the motor vehicle in a vertical direction when negotiating a terrain by adding power to thereby influence a control variable of the suspension, wherein the control variable of the active suspension is a path traveled in the vertical direction or the control variable of the active suspension is a force acting in the vertical direction;

a control unit configured to determine a first signal of a velocity of the body in the vertical direction and a second signal of the control variable, said control unit further being configured to determine a value for a mechanical energy derived from the second signal to compare the mechanical energy with a predefined threshold value for the mechanical energy, and to determine a phase shift between the first and second signals, said control unit comparing a value of the phase shift with a predefined threshold value, identifying a presence of excitation of the vertical body movement when the value of the phase shift deviates from the predefined threshold value at least by a tolerance value or when the value of the phase shift is greater than the predefined threshold value so that an excitation index has the value one.

10. The operating system of claim 9 , further a comprising a high-pass filter and a low-pass filter for filtering each of the first and second signals, said high-pass filter and low-pass filter having a cut-off at 1 Hz.