Apparatus and method using a lock-in amplifier in the control of a periodic force applied to a moving part
AssigneeMolins Limited
InventorsDavid Christopher Miller Carter, Peter Nicholas Collett
Life of this patent
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Abstract
An application for periodically applying a controllable force to a movable part has a force applying member, particularly for cutting a web, and a driver for driving the force applying member. The driver is controlled by a force-indicating signal produced by a lock-in amplifier to which a force-responsive signal and a reference signal are inputted. The lock-in amplifier operates to eliminate or reduce any noise present in the force-responsive signal.
Claims15
A method for periodically applying a controllable force to a moving part by means of a force-applying member, comprising the steps of producing an electrical force-indicating signal which is indicative of the force applied by the force-applying member, and using said force-indicating signal to control said applied force, the force-indicating signal being produced with the aid of a lock-in amplifier to which a force-responsive signal is applied together with a reference signal, whereby any noise element in the force-responsive signal is eliminated or reduced by the lock-in amplifier.
A cutting apparatus for cutting a moving web, said cutting apparatus comprising:
- a web support member for supporting said moving web;
- a force-applying member which is periodically driven towards said web support member so as to apply a force to said web whereby the web is crush cut between said force-applying member and said web support member;
- a first drive for driving said force-applying member;
- a second drive for positioning said force-applying member relative to said web support member;
- and
- a control circuit for controlling said second drive whereby to control the force applied by said force applying member to said web, said control circuit including a lock-in amplifier which receives a first signal which is a function of said force applied by said force-applying member and a reference signal, and outputs a second signal which is a function of said force applied by said force-applying member such that any noise present in said first signal is not present or is substantially reduced in said second signal, said control circuit being arranged to use said second signal to control said second drive.
Apparatus for periodically applying a controllable force to a moving part, said apparatus comprising a force-applying member, and means for producing an electrical force-indicating signal indicative of the force applied to said moving part by the force-applying member and for controlling the force-applying member using said force-indicating signal so as to control the forces applied by said force-applying member to the moving part, said force-indicating signal being produced with the aid of a lock-in amplifier to which is applied a force-responsive electrical signal together with a reference signal, whereby any noise element in said force-responsive electrical signal is eliminated or reduced by the lock-in amplifier.
Apparatus for periodically applying a controllable force to a moving part, said apparatus comprising:
- a force-applying member;
- an ultrasonic driver which is responsive to an ultrasonic drive signal to cause ultrasonic vibration of said force-applying member whereby said force-applying member periodically applies a force to said moving part;
- and
- a control circuit which derives a force-affected signal and a reference signal from said drive signal and comprises a lock-in amplifier which receives said force-affected signal and reference signal and produces an output signal which is used to control the force applied by said force-applying member, said lock-in amplifier operating to substantially eliminate or reduce any noise element in said force-affected signal.
Dependencies are inferred from the claim text.