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Control arrangement for a propulsion unit for a self-propelled floor care appliance

  • US 7,725,223 B2
  • Filed: 09/26/2006
  • Issued: 05/25/2010
  • Est. Priority Date: 09/30/2003
  • Status: Active Grant
First Claim
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1. A self-propelled floor care appliance controlled by a moveable handgrip comprising:

  • a drive motor to control the movement of the floor care appliance;

    a Hall effect sensor in operative communication with the handgrip, said Hall effect sensor configured to generate a Hall voltage based on the movement of the handgrip in at least a limited reciprocal rectilinear motion;

    a microprocessor coupled to said Hall effect sensor, and to store a response characteristic, wherein said response characteristic comprises a logistic function;

    a selection switch coupled to said microprocessor to select one of at least two response characteristics for at least direction and speed of the appliance maintained by said microprocessor;

    a lookup table maintained by said microprocessor, said lookup table associating a plurality of predetermined digital Hall voltage levels with predetermined pulse width modulation (PWM) output levels in accordance with a logistic response characteristic including at least both direction of movement of the appliance and speed of the appliance;

    wherein said microprocessor outputs a pulse width modulation (PWM) control signal to said drive motor, such that said PWM control signal includes one of said PWM output levels associated with said Hall voltage output by said Halt effect sensor in accordance with said lookup table;

    wherein said logistic function comprises a hyperbolic tangent function having the formula;

    Tanh

    ( t )
    = e t - e - t e t + e - t .

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