Abstract:
A mechanism for compensating power to a motor or actuator. Compensation may counter the effects of changing voltage levels of power to the motor and varying temperatures at the motor. An output of a wave generator may be input to a comparator along with a level of voltage representing the temperatures and voltage levels. An output may be a power signal for driving the motor at a constant speed and/or torque which can increase a maintenance-free lifetime of the motor and actuator.

Description:
BACKGROUND 
     The present disclosure pertains to power supplies and particularly to power supplies having compensated outputs. More particularly, the disclosure may pertain to power supplies for actuators. 
     SUMMARY 
     The disclosure reveals a mechanism for compensating power to a motor or actuator. Compensation may counter the effects of changing voltage levels of power to the motor and varying temperatures at the motor. An output of a wave generator may be input to a comparator along with a level of voltage representing the temperatures and voltage levels. An output may be a power signal for driving the motor at a constant speed and/or torque which can increase a maintenance-free lifetime of the motor and actuator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a diagram of a drive circuit having a compensated output; 
         FIG. 2  is a diagram of a graph showing a voltage from a waveform generator to an input of a comparator and a voltage level signal from a calculation circuit to an input of the comparator; 
         FIG. 3  is a diagram of a motor power calculation circuit; and 
         FIG. 4  is a diagram of a circuit having a processor or computer used for compensating power to a motor. 
     
    
    
     DESCRIPTION 
     The present system and approach may incorporate one or more processors, computers, controllers, user interfaces, wireless and/or wire connections, and/or the like, in an implementation described and/or shown herein. 
     The present description may provide one or more illustrative and specific examples or ways of implementing the present system and approach. There may be numerous other examples or ways of implementing the system and approach. 
     The mechanism disclosed here may have application to actuators and particularly to actuators in heating, ventilation and air conditioning (HVAC) systems for buildings. Actuators may have a range of device input voltages (AC or DC) that they will accept for operation. In addition, they may have a wide range of temperatures that they need to operate in. But, the performance of designs may vary considerably as these factors change, even when they are within the specifications of the device. Often times, when these devices are given input voltage towards their high limit, they may drive at a faster rate and higher torque. When they are given input voltage towards their low limit, they may drive slower with less torque. The problem with torque and speed being affected by input voltage is that the actuator&#39;s performance for the end user may be a function of the voltage source for the device. This could be undesirable as the actuator should have consistent and repeatable operation for any user when the input voltage is within the wide range of input voltage specified for the device. Also, a device that consistently drives at higher speed and torque may encounter increased wear over time compared to a device that drives with nominal speed at nominal input voltage. A constant drive speed may ensure that the actuator opens in the same amount of time and at the same sound-decibel level over varying input voltages, increasing a perception of quality. 
     Varying device temperature may also have an effect on torque and speed. As the device temperature increases, the resulting drive speed and torque may decrease. As the device temperature decreases, driving speed and torque may increase. The problem with torque and speed being affected by temperature is that the actuator&#39;s performance may be a function of the climate of the installation location (e.g., rooftop in Arizona compared to Alaska). This may be also undesirable as the actuator should have consistent and repeatable operation when the temperature is within the specification for the device. 
     Finally, having the drive torque of the actuator vary based on input voltage and temperature makes the mechanical design of the actuator more complicated and costly. Large variances in internal loading have to be accounted for in the gear, spring and overall tolerance and spacings if the torque varies over voltage input and temperature conditions. 
     The present circuit may solve the problem by compensating for device input voltage (AC and DC) and temperature, simultaneously. Specifically, the present approach may sample the device input voltage and temperature, and then compute a percentage of power to be delivered to the motor as a function of those inputs. For example, for higher input voltage, the circuit may reduce power to the motor to keep speed and output torque constant. At higher temperature, the circuit may increase power to the motor to keep speed and output torque constant. The circuit may consist of analog and/or digital components to actively and continuously make this computation, for continuous compensation. 
     One way to implement the circuit may be to use a circuit which uses a standard triangle wave generator and a comparator to make a temperature compensated PWM signal, which drives the motor. The analog components highlighted are the present circuit that allows constant motor speed and torque over change of input voltage and temperature. 
     Another approach may be to use a digital microcontroller that controls the motor power. The microcontroller may sample the input voltage and the device temperature. Based on these readings, hardware and/or software may compensate the motor power to keep the actuator speed and torque constant over temperature and input voltage. By utilizing the processing approach, the overall mechanical design may be simplified since variances in temperature and input voltage no longer necessarily vary the mechanical workings of the device. 
       FIG. 1  is a diagram of a drive circuit  11  for compensating a drive signal on an output  12  of circuit  11  for an actuator  22  in view of a changing temperature of an environment of actuator  22  and a varying supply voltage Vcc. A voltage Vo from a motor power calculation circuit  21  may be provided to an inverting input  13  of a comparator  14  in drive circuit  11 . A triangle waveform  16  of voltage from triangle wave generator  17  may be provided to a non-inverting input  15 . 
       FIG. 2  is a diagram of a graph showing a triangle wave voltage  16  from generator  17  to input  15  of comparator  14  and a voltage level signal  18  from calculation circuit  12  to input  13  of comparator  14 . Signal  18  may move up and down relative to waveform signal  16  as indicated by arrow  36 . When a point of wave  16  is positioned below voltage  18 , output  12  has a signal  23  situated at a low level which may be a zero or minus voltage, since signal  18  overrides signal  16  and the positive voltage signal  18  is inverted to a negative signal because of the inverting input. When a point of wave  16  is positioned at a positive voltage above voltage  18 , output  12  has a signal  23  situated at a high level which may be a positive voltage, since the input is a non-inverting input that retains the positive polarity aspect of the triangular wave  16 . Signal  23  may appear to be a series of square-like pulses  24  on output  12 . The pulses  24  may be widened or narrowed in shape, as indicated by arrow  37 . Pulses  24  may be regarded as a pulse width modulated (PWM) signal  23 . Pulses  24  may be as wide as the points at which the triangular wave  16  is above voltage level  18 . 
     As voltage  18  increases at input  13 , then the positive pulse  24  becomes narrower and thus the power from output  12  to an actuator or DC motor  22  of, for example, an actuator, may decrease. Voltage  18  may appear to correlate with the Vcc supply that would be provided to the power calculation circuit  21 . Also, as the ambient temperature of motor  22  increases, then the voltage  18  output level may decrease. The decrease in voltage  18  level may result more of the triangular wave signal  16  being above the voltage  18 . Thus, positive pulse of signal  23  would be wider and provide more power to motor  22 . The extra power would compensate for increased temperature which would cause the motor to slow down slightly without the increased power. In this way, the motor speed may remain constant due to an increase in power to it in view of increased temperature. 
       FIG. 3  is a diagram of the motor power calculation circuit. The component values are illustrative examples but could be other values. A 24.9K ohm resistor  25  may have one end connected to Vcc of a power supply and another end connected to a terminal  26 . Terminal  26  may be the output of circuit  21  that provides voltage  18  to input  13  of comparator  14 . A 2.21K ohm resistor  27  may have one end connected to terminal  26  and another end connected to a cathode of an adjustable zener  28 . Adjustable zener  28  may be a model LM431 available from various semiconductor vendors. The anode of adjustable zener  28  may be connected to a ground  34 . The other end of resistor  27  may also be connected to one end of a 12.1K ohm resistor  29 . The other end of resistor  29  may be connected to one end of a 4.02K ohm resistor  31  and to one end of a 10K to 20K ohm resistor  32  having a negative temperature coefficient (NTC). The other end of resistor  31  and the other end of resistor  32  may be connected to a third terminal of adjustable zener  28 , with the cathode and anode being the other two terminals. Resistor  32  may have a B-constant of the NTC of 3380K ohms and a resistance of 10K ohms at an ambient temperature. A virtually constant 2.54 volts may appear between the third terminal and the anode during normal operation of adjustable zener  28 . A 10K ohm resistor  33  may have one end connected to the third terminal of adjustable zener  28  and the other end to the anode of adjustable zener  28 . 
     The circuit portion incorporating resistors  29 ,  31 ,  32  and  33  and adjustable zener  28  may have the third terminal being referred to as a voltage reference. 
       FIG. 4  is a diagram of a circuit having a processor or computer  41  used for controlling power to a motor  42 . Temperature of motor  42  may be detected by sensor  43  and provided to computer  41 . The input voltage may be detected by a sensor  44  and be input to computer  41 . Based on the temperature and input voltage detected, computer  41  may provide compensation for the power of motor  42  to keep an actuator speed and torque constant over changes in temperature and input voltage. The motor may be used for or be a part of an actuator. An indication of a speed (via, e.g., a tachometer) of the motor may provided to the processor or computer that has, for instance, already adjusted the voltage to the motor according to the temperature of the motor and voltage of the power supply, to diagnostically confirm an adjustment of the voltage to the motor according to the temperature of the motor and the voltage of the power supply. The tachometer indication may instead precede the adjustment according to the voltage and temperature for confirmation or diagnostic purposes. 
     To recap, a power compensator for an actuator of a heating, ventilation and air conditioning system (HVAC), may incorporate a first source of voltage, a second source of voltage, and an operational amplifier. The first source may have a waveform generator. The second source of voltage may have a calculation circuit for power to an actuator. An output of the first source of voltage may be connected to a non-inverting input of the operational amplifier. An output of the second source of voltage may be connected to an inverting input of the operational amplifier. An output of the operational amplifier may be a third source of voltage that goes to the actuator. 
     An output of the third source of voltage may maintain a constant speed or torque of the actuator. An output of the second source of voltage may provide a signal that has an amplitude incorporating compensation in the output of the operational amplifier, for temperature of the actuator and a voltage of a power supply for the actuator. 
     The calculation circuit may incorporate a temperature sensitive impedance unit and a voltage sensitive unit. The temperature sensitive impedance unit may detect a temperature of the actuator. The voltage sensitive unit may detect an amount of the voltage of the power supply for the actuator. 
     The output of the first source of voltage may have a periodically varying waveform. The output of the third source of voltage may incorporate a pulse width modulated waveform. The operational amplifier may incorporate a gain configuration that makes the operational amplifier a comparator. 
     The output of the first source of voltage may have a triangular waveform. The output of the second source of voltage may increase in amplitude when the temperature of the actuator increases. The output of the second source of voltage may decrease in amplitude when the voltage of the power supply for the actuator increases. 
     The second source of voltage may incorporate a first impedance having one end connected to the input voltage of the power supply for the actuator and another end connected to the output of the second source of voltage, a second impedance having one end connected to the output of the second source of voltage and another end connected to a cathode of an adjustable zener, a third impedance having one end connected to the cathode of the adjustable zener and having another end connected to a reference voltage terminal of the adjustable zener, and a fourth impedance having a first end connected to the reference voltage terminal of the adjustable zener and having another end connected o an anode of the adjustable zener. The third impedance may have a negative temperature coefficient. 
     A system, for actuator speed control, may incorporate a variable amplitude wave generator, a power calculation circuit, and a comparator having a first input connected to an output of the variable amplitude wave generator, a second input connected to an output of the power calculation circuit, and an output for connection to a motor of an actuator. The variable amplitude wave may be periodic. 
     The power calculation circuit may incorporate a temperature sensitive component and a voltage sensitive component. The temperature sensitive component may detect a temperature of the motor. The voltage sensitive component may detect a voltage of a power supply for the motor. The output of the comparator may provide a compensated waveform of power for the motor. 
     The power calculation circuit may provide an output that compensates for the temperature of the motor and the voltage of a power supply for power to the motor. 
     The temperature sensitive component may cause an increase of output of the power calculation circuit when an increased temperature is detected by the temperature sensitive component. The voltage sensitive component may cause a decrease of output of the power calculation circuit when an increase of voltage is detected by the voltage sensitive component. 
     The power calculation circuit may incorporate an adjustable zener, a first impedance component having a first terminal connected to a cathode of the adjustable zener, and having a second terminal connected to a reference voltage terminal of the adjustable zener, and a second impedance component having a first terminal connected to the second terminal of the first impedance component and having a second terminal connected to an anode of the adjustable zener. 
     The power calculation circuit may further incorporate an impedance divider component having a first terminal for connection to the voltage of the power supply, a second terminal connected to the cathode of the adjustable zener, and having an output terminal as an output of the power calculation circuit. 
     The variable amplitude wave generator may output a triangular waveform of voltage at a predetermined frequency. The power calculation circuit may output a voltage that has an amplitude adjusted according to the temperature sensitive component and the voltage sensitive component. 
     An output of the comparator may incorporate a square wave that has a width which varies according to the amplitude of the voltage from the power calculation circuit. The wave may have other shapes. 
     The output of the comparator may be a pulse width modulated signal. The pulse width may be modulated to increase or decrease power to the motor according to the voltage of the power supply for the motor and the temperature of the motor. 
     A mechanism, for controlling power to a motor, may incorporate a processor, a temperature sensor that detects temperature of a motor for an actuator, and a voltage sensor that detects a voltage of a power supply for the motor. The temperature sensor may be connected to the processor. The voltage sensor may be connected to the processor. The processor may provide a signal that adjusts a voltage to the motor according to the temperature of the motor and a voltage of the power supply. 
     The processor may incorporate a program that calculates the voltage to the motor according to the temperature of the motor and the voltage of the power supply. 
     The voltage to the motor may be adjusted for the motor to operate the actuator at a constant speed. 
     The mechanism, for controlling power to a motor, may further incorporate a speed indicator such as a tachometer connected to the motor and the processor. An indication of a speed of the motor may be provided by the speed indicator to the processor that adjusts the voltage to the motor according to the temperature of the motor and voltage of the power supply, to diagnostically confirm an adjustment of the voltage to the motor according to the temperature of the motor and the voltage of the power supply. 
     In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
     Although the present system and/or approach has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the related art to include all such variations and modifications.