Encoderless motor with improved quantization and methods of use and calibration

Abstract

A DC electric motor having a stator mounted to a substrate, the stator having a coil assembly having a magnetic core, a rotor mounted to the stator with permanent magnets distributed radially about the rotor, the permanent magnets extending beyond the magnetic core, and sensors mounted to the substrate adjacent the permanent magnets. During operation of the motor passage of the permanent magnets over the sensors produces a substantially sinusoidal signal of varying voltage substantially without noise and/or saturation, allowing an angular position of the rotor to be determined from the sinusoidal signals by utilizing a transformation matrix or piece-wise algorithm applied in substantially linear portions of the sinusoidal signals without requiring use of additional hardware encoder or position sensors and without requiring noise-reduction or filtering of the signal.

What is claimed is: 
     
         1 . An n-phase encoder for use in a mechatronic system, the encoder comprising:
 a movable element that applies a magnetic field with period, S, the period representing a total displacement;   a stationary support with n magnetic field sensors mounted thereon and positioned on the stationary support so as to measure the magnetic field imparted by the movable element, wherein n is greater than 1; and   a processor communicatively coupled to the n magnetic field sensors and configured to determine displacement of the movable element based on n signals from the n magnetic field sensors by processing the n signals utilizing a transformation matrix.   
     
     
         2 . The encoder of  claim 1 , wherein the total displacement is 2π radians of a field angle ϕ. 
     
     
         3 . The encoder of  claim 2 , wherein the processor is configured to process the n signals from the n sensors by:
 computing a sine and cosine of the field angle, ϕ, by pre-multiplying an n-by-1 vector by a 2-by-n mathematical transformation matrix, M; and   computing the field angle, ϕ, as ϕ=tan−1(sin(ϕ),cos(ϕ)).   
     
     
         4 . The encoder in  claim 1 , where S is a rotary displacement. 
     
     
         5 . The encoder in  claim 1 , where S is a linear displacement. 
     
     
         6 . The encoder in  claim 3 , wherein the mathematical transformation, M, is configured such that calculation of the field angle, ϕ, is independent of an amplitude and bias of the magnetic field sensors. 
     
     
         7 . The encoder in  claim 1 , where the magnetic field sensors are uniformly distributed within the period, S. 
     
     
         8 . The encoder  claim 1 , where the system is configured such that the applied magnetic field is represented by a sum of first and at least one of higher-order harmonics. 
     
     
         9 . The encoder of  claim 1 , wherein the processor is configured to:
 store a runout represented by a spatially-varying signal representing a difference between a true field angle and a sensed field angle and utilizes the runout to compensate for the difference thereby removing any runout error.   
     
     
         10 . The encoder in  claim 1 , where the encoder is utilized in a BLDC motor configured for operation of a mechatronic system within a diagnostic assay system. 
     
     
         11 . The encoder in  claim 10 , wherein the mechatronic system of the diagnostic assay system comprises any of: a syringe, valve, cartridge loading or door mechanism. 
     
     
         12 . A processing method comprising:
 providing an n phase encoder of a mechatronic system that includes a movable element that applies a magnetic field with period, S, the period representing a total displacement, and a stationary support with n magnetic field sensors mounted thereon and positioned on the stationary support so as to measure the magnetic field imparted by the movable element, wherein n is greater than 1;   obtaining signals from the n magnetic field sensors corresponding to the measurements of the magnetic field imparted by the movable element; and   processing n signals from the n magnetic field sensors by utilizing a transformation matrix to determine a displacement of the movable element.   
     
     
         13 . The processing method of  claim 12 , wherein the total displacement is 2π radians of a field angle ϕ. 
     
     
         14 . The processing method of  claim 13 , wherein processing the signals from the n sensors comprises:
 computing a sine and cosine of the field angle, ϕ, by pre-multiplying an n-by-1 vector by a 2-by-n mathematical transformation matrix, M; and   computing the field angle, ϕ, as ϕ=tan−1(sin(ϕ),cos(ϕ)).   
     
     
         15 . The processing method of  claim 12 ,
 wherein the processing comprises normalizing an amplitude of at least one of the signals from the n magnetic field sensors to an arbitrary value.   
     
     
         16 . The processing method of  claim 15 ,
 wherein processing of the signals further comprises subtracting a signal bias of at least one of the signals from the n magnetic field sensors before a normalization operation.   
     
     
         17 . The processing method of  claim 16 ,
 wherein processing further comprises storing in memory or outputting to the mechatronic system, one or more signal bias coefficients   
     
     
         18 . The processing method of  claim 12 , where S is a rotary displacement. 
     
     
         19 . The processing method in  claim 12 , where S is a linear displacement. 
     
     
         20 . The processing method in  claim 12 , wherein processing n signals comprises processing only a substantially linear portion(s) of the signals. 
     
     
         21 . A calibration method for an n-phase encoder as in  claim 1  in which the amplitude, bias and phase-shift of the signal of the n sensors is computed and stored in a memory of the encoder or the mechatronic system in which it is employed. 
     
     
         22 . The calibration method of  claim 21 , wherein a transformation matrix, M(ϕ)), specific to the mechatronic system accounts for irregularities or otherwise actual phase-to-phase angle offsets.