Force counterbalance system and method

1 . A head-mountable device (HMD), comprising:

a housing;

a display coupled to the housing;

a counterbalance coupled to the display, the counterbalance comprises a cam; and

an energy storage device coupled to the display, the energy storage device configured to apply a force to the display;

a profile of the force being configured to vary non-linearly as a position of the display relative to the housing changes; and

a position of a component of the counterbalance configured to adjust based on a change to the profile of the force.

2 . The HMD of claim 1 , wherein:

the energy storage device is configured to apply the force to the display through the cam; and

the profile of the force is configured to vary according to a surface profile of the cam.

3 . The HMD of claim 2 , wherein the surface profile comprises a plurality of dimples.

4 . The HMD of claim 2 , wherein the energy storage device comprises a mechanical spring.

5 . The HMD of claim 2 , wherein the energy storage device is coupled to the surface profile of the cam by a bearing or bushing configured to roll along the surface profile.

6 . The HMD of claim 1 , wherein the energy storage device comprises a non-linear energy storage device.

7 . The HMD of claim 1 , further comprising a cover coupled to the display, wherein:

the cover is configured to apply a cover force to the display; and

the profile of the force is configured to counterbalance the cover force applied to the display by the cover.

8 . An electronic device comprising:

a display;

an adjustment mechanism configured to move the display; and

a cam mounted to the display and configured to apply an offload force to the display, the cam comprising an adjustable surface, wherein:

the offload force is configured to vary based on a surface profile of the cam; and

the offload force is configured to minimize a force applied by the adjustment mechanism to move the display.

9 . The electronic device of claim 8 , wherein the offload force is further configured to vary non-linearly as the display moves through a range of motion.

10 . The electronic device of claim 8 , wherein the offload force is configured to vary dynamically as characteristics of the electronic device change.

11 . The electronic device of claim 8 , further comprising a manual actuator configured to actuate the adjustment mechanism.

12 . The electronic device of claim 8 , further comprising a motor configured to actuate the adjustment mechanism.

13 . The electronic device of claim 8 , wherein the offload force is applied to the display through the cam by a passive energy storage device.

14 . The electronic device of claim 8 , wherein the offload force applied to the display is configured to vary from a first direction to a second direction opposite the first direction as the display moves in a single direction through a range of motion.

15 . A method of counterbalancing a force, the method comprising:

determining a profile of a force acting on a display;

determining a surface profile for a cam based on the profile of the force, the cam is mounted to the display;

applying an offload force to the display through a counterbalance that comprises the cam, wherein the offload force varies non-linearly based on the surface profile; and

adjusting a position of a component of the counterbalance based on a change to the profile of the force acting on the display.

16 . The method of claim 15 , wherein the change is detected based on environmental conditions of the display or an age of the display.

17 . The method of claim 15 , wherein adjusting the position of the component comprises changing the surface profile of the cam.

18 . The method of claim 15 , wherein the surface profile is determined to minimize a difference between the force and the offload force throughout a travel of the display.

19 . The method of claim 15 , wherein the profile of the force is determined by measuring the force as the display moves through a range of motion.