In or relating to stairlifts
The invention provides a method and apparatus for continuously adjusting the speed of a stairlift in response to a number of operating parameters such as battery voltage and motor current draw. The method preferably further includes monitoring the speed of a reference point on a stairlift chair and comparing this with a maximum permissible speed.
1. A method of controlling the speed of a stairlift, the stairlift having:
a rail having at least one bend therein;
a carriage mounted on the rail;
an electric carriage motor operable to move the carriage along the rail;
at least one battery to power the electric carriage motor; and
a chair mounted on the carriage,
the method comprising:
generating a first signal representative of current drawn by the carriage drive motor;
generating a second signal representative of a voltage level in the at least one battery or the power draw from the battery;
generating one or more third signals representative of a speed of a reference point on the chair, the one or more third signals being combined with the first and second signals for controlling a speed of the electric carriage motor;
and controlling the speed of the electric carriage motor based on the combined first, second and one or more third signals.
2. The method according to claim 1 , wherein the carriage is rotatable with respect to the chair at a relative angular velocity when the carriage rotates relative the chair, the method including generating a signal representative of the relative angular velocity between the carriage and the chair as the carriage moves through a transition bend in the rail.
3. The method according to claim 2 , further including comparing the relative angular velocity with the speed of the electric carriage motor and, if necessary, adjusting the speed of the electric carriage motor to ensure that the chair is maintained substantially level.
4. The method according to claim 1 , further including generating a signal representative of angular velocity of the carriage as the carriage moves through a horizontal bend in the rail.
5. The method according to claim 2 , wherein measurement of the angular velocity of the carriage are effected using one more gyroscopes mounted in or on the carriage and/or the chair.
6. The method according to claim 5 , wherein signals from the one or more gyroscopes are processed to establish the speed of a reference point on the chair.
7. The method according to claim 1 , further comprising adjusting the speed of the carriage pre-emptively having regard to the position of the carriage on the rail.
8. The method according to claim 7 , comprising learning and storing in a memory, acceptable speed changes at various positions on the rail.
9. A stairlift, including:
a rail having at least one bend therein;
a carriage mounted on the rail;
an electric carriage motor operable to move the carriage along the rail;
at least one battery to power the electric carriage drive motor; and
a chair mounted on the carriage;
the stairlift further including a speed control facility configured to:
generate a first signal representative of current drawn by the electric carriage drive motor,
generate a second signal representative of a voltage level in the at least battery or the power draw from the battery; and
generate one or more third signals representative of the speed of a reference point on the chair, and to apply the one or more third signals, along with the first and second signals for controlling a speed of the carriage drive motor;
and controlling the speed of the electric carriage motor based on the combined first, second and one or more third signals.
10. The stairlift according to claim 9 , wherein the speed control facility includes one or more gyroscopes mounted on or in the carriage and/or the chair to generate the first signal.
11. The stairlift according to claim 9 , wherein the speed control facility includes a 3-axis gyroscope mounted in the carriage.