Fall prevention system

1. A system for fall prevention for a user, comprising:

one or more sensors configured to be attached to respective portions of the body of a walking user to measure movements of a moving center of mass of the user and a moving base of support of the body and to translate the measured movements into signals, the base of support of the user being a surface defined by a step width and a step length of the user when walking; and

a controller configured to receive the signals and to determine a risk of falling of the walking user by estimating a difference between a trajectory of the moving center of mass of the user relative to a trajectory of the moving base of support of the body from the signals.

2. The system as claimed in claim 1 , wherein the controller is further configured to:

determine whether the signals have a reoccurring pattern over time in multi-dimensional space; and

based on periodicity of the reoccurring pattern, determining whether the user is in a walking steady state.

3. The system as claimed in claim 2 , wherein the controller is further configured to:

determine periodicity of the signals when the user is in the walking steady state by detecting peaks in at least one of the movement signals to delineate individual steps.

4. The system as claimed in claim 3 , wherein the controller is further configured to:

from the signals for each step, determining (1) the step size and the step width and (2) a location of the center of mass; and

determining whether the center of mass is aligned within the base of support.

5. The system as claimed in claim 4 , wherein the controller is further configured to:

from the signals, determine a velocity of the center of mass and whether the center of mass is within the base of support; and

determining the risk of falling in response to one of:

the center of mass being outside the base of support and having a velocity which is insufficient to bring the center of mass back within the base of support, or

the center of mass is within the base of support and the velocity is outwards from the base of support.

6. The system as claimed in claim 1 , wherein the controller is further configured to:

from the signals, determine a velocity of the center of mass and whether the center of mass is within the base of support; and

determining the risk of falling in response to one of:

the center of mass being outside the base of support and having a velocity which is insufficient to bring the center of mass back within the base of support, and

the center of mass is within the base of support and the velocity is outwards from the base of support.

7. The system as claimed in claim 1 , wherein the one or more sensors include accelerometers, and the trajectories are estimated by integrating the signals from the accelerometers.

8. The system as claimed in claim 1 , wherein the one or more sensors include accelerometers, and the controller is configured to estimate the trajectory of the center of mass of the user relative to the trajectory of the base of support of the body by computing one of a Lyapunov exponent and a Floquet Multiplier from the movement signals.

9. A system for fall prevention for a user comprising:

one or more sensors configured for attachment to respective portions of a body of the user, the sensors being configured to measure movement of the respective portions of the body and to translate the measured movement into movement signals; and

a controller configured to:

receive the movement signals,

estimate a trajectory of a center of mass of the user from the movement signals,

estimate a trajectory of a base of support of the body from the movement signals, the base of support of the user being a surface defined by a step width and a step length of the user when walking,

determine a difference between the estimated trajectories of the center of mass of the user and of the base of support of the body of the user, and

determine a risk of falling from the difference between the trajectories.

10. The system as claimed in claim 9 , wherein the control unit is further configured to cause an alarm signal to be generated based on the determined risk of fall to alert the user or a caregiver.

11. The system as claimed in claim 9 , wherein the one or more sensors include a first accelerometer configured for attachment to an upper portion of the user's body for measuring movement of the upper portion of the body, and the controller is configured to estimate the trajectory of the center of mass of the user from the signals from the first accelerometer.

12. The system as claimed in claim 11 , wherein the controller is further configured to estimate the trajectory of the base of support of the body using the signals from the first accelerometer.

13. The system as claimed in claim 11 , wherein the system comprises at least one second accelerometer configured for attachment to a lower portion of the users body to output signals representing movement of the base of support of the body during walking, and the controller is further configured to estimate a trajectory of the base of support from the second accelerometer output signals.

14. The system as claimed in claim 11 , wherein the one or more sensors include another accelerometer configured for attachment to a lower portion of the user's body and wherein the controller is further configured to:

from the signals from another accelerometer, determine the step length and the step width of the user when walking and a location of the base of support;

from the signals from the first accelerometer, determine a velocity and location of the center of mass of the user; and

determining the risk of falling in response to one of:

the center of mass being outside the base of support and having a velocity which is insufficient to bring the center of mass back within the base of support, and

the center of mass is within the base of support and the velocity is outwards from the base of support.

15. A method for fall prevention for a user comprising, with a controller:

receiving movement signals measured by one or more sensors configured for attachment to respective portions of a body of the user and for measuring movement of the respective portions of the body and translating the measured movement into the movement signals;

estimating a trajectory of a center of mass of the user from the movement signals;

estimating a trajectory of a base of support of the body from the movement signals, the base of support of the user being a surface defined by a step width and a step length of the user when walking;

determining a difference between the estimated trajectories of the center of mass of the user and the base of support of the body; and

determining a risk of falling from the difference between the trajectories.

16. A non-transitory computer-readable medium carrying instructions for controlling a processor controller to perform the method as claimed in claim 15 .

17. The method as claimed in claim 15 , further including, with the controller:

from the movement signals, determining a velocity of the center of mass and whether the center of mass is within the base of support;

determining the falling risk based on one of:

the center of mass being outside the base of support and having a velocity which is insufficient to bring the center of mass back within the base of support, and

the center of mass is within the base of support and the velocity is outwards from the base of support.

18. The method as claimed in claim 15 , further including, with the controller:

determining whether the movement signals have a reoccurring pattern over time in a multi-dimensional space;

based on the periodicity of the reoccurring pattern, determining whether the user is in a walking steady state;

detecting peaks in the motion signals to delineate individual steps;

determining the step length and the step width; and

determining whether the center of mass is aligned within the base of support.