WO1997031216A1

WO1997031216A1 - Improvements in or relating to camera mounting pedestals

Info

Publication number: WO1997031216A1
Application number: PCT/GB1996/002792
Authority: WO
Inventors: Richard Arthur Lindsay
Original assignee: Vitec Group, Plc
Priority date: 1996-02-26
Filing date: 1996-11-14
Publication date: 1997-08-28
Also published as: GB2310410A; AU7580496A; GB9603986D0

Abstract

The disclosure relates to a camera mounting pedestal having a rolling base (10) mounted on spaced steerable individually suspended wheel units (12). The suspension for each unit comprises a relatively soft, damped spring (26) for absorbing higher frequency wheel movements and thereby preventing such movement from being transmitted to the base, and a displacement actuator (22) in series with the spring to apply a variable force between the wheel and base. The actuators for the wheel units have a control system including gyroscope means (15) responsive to tilting of the base about any horizontal axis (15a) and accelerometer means (14) responsive to vertical movement of the base to operate the actuators so as to neutralise transmission of lower frequency movements from the wheels to the base.

Description

IMPROVEMENTS IN OR RELATING TO CAMERA MOUNTING PEDESTALS

This invention relates to camera mounting pedestals including dollies for supporting a T.V., video or cinematographic camera for movement whilst in use over any surface, typically a studio floor or outside over the ground.

Conventionally such pedestals have rigid mounted wheel units and so any irregularities in the floor or ground over which the pedestal moves are transmitted directly to the pedestal and therefore to the camera supported on the pedestal. Irregularities can vary from surface roughness, cables or other minor obstructions laid on the floor to gradients or cambers in the floor. Such irregularities will impose disturbing forces on the wheel or wheels with frequencies which will vary with the nature of the irregularity and the speed of the pedestal.

It is an object of this invention to minimise the imposition of disturbing forces on the pedestal as it moves over a surface on which there are irregularities.

This invention provides a camera mounting pedestal having a rolling base mounted on spaced steerable individually suspended wheel units, the suspension for each unit comprising a relatively soft, damped spring for absorbing higher frequency wheel movements and thereby preventing such movement from being transmitted to the base, and a displacement actuator in series with the spring to apply a variable force between the wheel and the base, the actuators for said wheel units having a control system including means responsive to tilting of the base about any horizontal axis and means responsive to vertical movement of the base to operate the actuators to neutralise transmission of lower frequency movements from the wheels to the base.

Preferably the displacement actuators in the wheel unit suspensions comprise linear actuators.

In addition transducers may be provided for determining the vertical positions of the wheels in the range of travel provided by the displacement actuators so that the control system can maintain the base at a required height above the ground.

In any of the above arrangements the control system may include inclinometer means for detecting tilt of the pedestal out of the vertical to adjust the actuators to maintain the pedestal in a predetermined attitude.

In any of the above arrangements the pedestal may have an upstanding column for mounting a camera at its upper end and the control system is arranged to maintain the column vertical in response to signals received from the inclinometer means.

Preferably the pedestal has a generally triangular form base with three individually steerable wheel units at the apices of the base.

The following is a description of a specific embodiment of the invention, reference being made to the accompanying drawings in which; Figure 1 is a diagrammatic view of a lower part of a camera mounting pedestal; and

Figure 2 is a detailed view of the suspension of one wheel unit of the pedestal.

Referring firstly to Figure 1 of the drawings, there is shown a camera mounting pedestal comprising a generally triangular form base 10 having a body 11 and chassis on which the body is mounted with steerable wheel units 12 at the apices of the chassis mounted on suspension arrangements which will be described with reference to Figure 2 below.

At the centre of the body there is an upright column, the lower part of which is indicated at 13 which embodies an accelerometer 14 for detecting movements of the pedestal in a vertical sense and gyroscope means 15 for detecting pitch and roll of the pedestal, as indicated at alpha and theta. In addition an inclinometer 15a is provided to indicate when the column of the pedestal is out of vertical. The accelerometer, gyroscope means and inclinometer provide input to a control system for the pedestal in the form of a micro-processor (not shown) .

Reference is now made to Figure 2 of the drawings which shows a part of the pedestal chassis 16 at one apex of the pedestal on which a wheel unit 12 is mounted. The wheel unit has an axle 17 mounted in a housing 18 and constrained horizontally by a pair of compression springs 19 and a damper 20 to provide a degree of compliance in the horizontal direction in the event that the wheel encounters an obstruction in its path of movement to eliminate some of the high frequency movements transmitted to the suspension. The housing 18 of the axle is mounted on the lower end of a vertical strut 21, the upper end of which is engaged by a linear displacement actuator 22 mounted in a housing 23 and controlled by the micro- processor of the control system. The linear drive mechanism adjusts the strut vertically with respect to the housing in the direction of the arrows 24 to respond to low frequency disturbances to the pedestal encountered in its movement over the floor as described below.

The position of the strut 24 in its vertical travel with respect to the housing 23 is determined by a linear displacement transducer indicated at 25 and again as described below, the control system is arranged to average displacement of the struts so that the clearance under the centre of the base returns to a nominal required distance.

The housing 23 is supported on the chassis 16 by means of a relatively soft spring 26 with a parallel damper 27 to allow vertical movement of the housing with respect of the chassis, as indicated by the arrow 28.

In moving over the floor, vertical forces are applied to the wheel units 12 by surface roughness and minor obstructions on the floor such as cables and varying gradients and camber in the floor. High frequencies input to the suspension systems for the wheel units of the order of twice the natural frequencies of the springs, typically at least 5 Hertz, are substantially absorbed by the relatively soft springs 26. Low frequency inputs reach the base and cause the base to pitch, roll, rise or fall or in combination thereof. The movement is detected by the gyroscope means 15 and accelerometer 14 which, in combination with the input from the linear displacement transducer at each wheel, cause the control system to operate the displacement actuators, to produce compensating movements of the wheel units to prevent or minimise disturbance to the pedestal and to maintain the clearance at the centre of the base at the required distance. Thus the linear actuators are adjusted by the control system to maintain the pedestal in a required attitude and height above the floor or ground over which it is moving. Usually, this will mean maintaining the pedestal base horizontal with the column of the pedestal vertical.

The inclinometer 15a caters for drift in the gyroscope means and provides a true vertical reference or datum for the control system.

Claims

1. A camera mounting pedestal having a rolling base mounted on spaced steerable individually suspended wheel units, the suspension for each unit comprising a relatively soft, damped spring for absorbing higher frequency wheel movements and thereby preventing such movement from being transmitted to the base, and a displacement actuator in series with the spring to apply a variable force between the wheel and base, the actuators for said wheel units having a control system including means responsive to tilting of the base about any horizontal axis and means responsive to vertical movement of the base to operate the actuators to neutralise transmission of lower frequency movements from the wheels to the base.

2. A camera mounting as claimed in claim 1, wherein the displacement actuators in the wheel unit suspensions comprise linear actuators.

3. A camera mounting pedestal as claimed in claim 1 or claim 2, wherein transducers are provided for determining the vertical positions of the wheels in the range of travel provided by the displacement actuators so that the control system can maintain the base at a required height above the ground.

4. A camera mounting pedestal as claimed in any of the preceding claims, wherein the control system includes inclinometer means for detecting tilt of the pedestal out of vertical and is arranged to adjust the actuators to maintain the pedestal in a predetermined attitude.

5. A camera mounting pedestal as claimed in claim 4, wherein the pedestal has an upstanding column for mounting a camera at its upper end and the control system is arranged to maintain the column vertical in response to signals received from the inclinometer means.

6. A camera mounting pedestal as claimed in any of the preceding claims having a generally triangular form base with three individually steerable wheel units at the apices of the base.

7. A camera mounting as claimed in any of the preceding claims, wherein the means responsive to tilting of the base comprise gyroscope means.

8. A camera mounting as claimed in any of the preceding claims, wherein the means responsive to mechanical movement of the base comprise accelerometer means.

9. A camera mounting as claimed in any of the preceding claims, wherein further damped spring means is provided to constrain movement of each wheel horizontally.