Pulse-width modulated amplifier for inverted planar motor

FIELD OF THE INVENTION

The present invention generally relates to an inverted planar motor of any type. The present invention specifically relates to a pulse-width modulated amplifier for use in an inverted planar motor, for example for the semiconductor industry.

BACKGROUND OF THE INVENTION

Inverted planar motors, particularly for the semiconductor industry, need to have high accelerations to achieve a high throughput. One way to achieve high accelerations is to increase the magnetic field. For example, an inverted planar motor known in the art employs a displacement device having magnets arranged in a two-dimensional pattern of rows and columns parallel to an X-direction and a Y-direction, respectively. The magnets in each row and column are arranged to a Halbach array to generate a very strong magnetic field, (i.e., the magnetic orientation of successive magnets in each row and each column rotates 90° counter-clockwise). The inverted planar motor further employs a coil actuator having two types of electric coils. One coil type has an angular offset of +45°, and the other coil type has an offset of -45° with respect to the X-direction. A controlled flow of current via amplifiers through the electric coils produces a desired magnetic interaction between the magnets and the electric coils.

Inverted planar motors, such as the aforementioned motor, need to have the capability of current sensors in accurately measuring current flowing through the electric coils and the capability of the amplifiers in measuring the K- factor of the electric coils related to the electric motive force. The present invention provides a new motor configuration for facilitating an accurate current passing through the electric coils to achieve an optimal actuation of the coils for purposes of moving the displacement device as desired.

SUMMARY OF THE INVENTION

One form of the present invention is a coil actuator comprising an electric coil and a current amplifier. The current amplifier is switchable between a K-factor measuring mode and a current measuring mode. The K-factor measuring mode includes the current

amplifier preventing a flow of current through the electric coil to facilitate a measurement of an electro motive force voltage indicative of a K-factor of the electric coil. The current measuring mode includes the current amplifier controlling a flow of current through the electric coil and a current sensor facilitating a measurement of the flow of current through the electric coil.

A second form of the present invention is an inverted planar motor employing the aforementioned coil actuator and a magnetic displacement device magnetically interactive with the coil actuator.

The foregoing forms and other forms of the present invention as well as various features and advantages of the present invention will become further apparent from the following detailed description of various embodiments of the present invention read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE EMBODIMENTS

FIG. 1 illustrates a block diagram of a first exemplary embodiment of an inverted planar motor in accordance with the present invention.

FIG. 2 illustrates a block diagram of a second exemplary embodiment of an inverted planar motor in accordance with the present invention.

FIGS. 3 and 4 illustrate a perspective top view and a perspective partial view respectively of an exemplary embodiment of the inverted planar motor illustrated in FIG. 1.

FIG. 5 illustrates a view of a schematic diagram of one embodiment of an amplifying circuit in accordance with the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, an inverted planar motor of the present invention employing a magnetic displacement device 10 and a coil actuator 20 are shown. Magnetic displacement device 10 includes a known arrangement of a magnetic plate 11, a carrier 12, a mirror block 13, a calibration unit 14 and a clamp 15. An example of carrier 12 and mirror block 13 are shown in FIG. 3.

Still referring to FIG. 1, coil actuator 20 includes electric coils 21 and Hall sensors 22 disposed within electric coils 21. The electric coils 21 and Hall sensors 22 (or alternatively magneto -restrictive sensors) are supported by a coil block 23 having cooling

channels for electric coils 21 depicted by the dashed arrow within coil block 23. An example of coil block 23 is shown in FIG. 3.

Still referring to FIG. 1, coil actuator 20 further includes current amplifying circuits and Hall electrodes 29. FIG. 1 shows the components of the current amplifying circuits relevant to the K-factor/coil current measuring modes of the present invention, which are current amplifier 26, current sensors 27, and dissipation elements 28 of current amplifiers

26 (e.g., Power-Fets, IGBTs or power bipolar transistors) as exemplarily shown in FIG. 4. The K-factor measuring mode involves current amplifiers 26 preventing a flow of current through coils 21 and a measurement of an electro motive force voltage for each electric coil 21 that is indicative of a K-factor of the electric coils as will be exemplarily described herein in connection with FIG. 5. The coil measuring mode involves one or more of current amplifiers 26 controlling a flow of current through respective electric coils 21 and corresponding current sensors 27 measuring the flow of the current through respective electric coils 21 as will be exemplarily described herein in connection with FIG. 5. For the coil current measuring mode, dissipation elements 28 are disposed within a secondary cooling body 24 having cooling channels for dissipation elements 28 depicted by the dashed arrow within secondary cooling body 24. Similarly, current sensors

27 are disposed within a primary cooling body 25 having cooling channels for current sensors 27 depicted by the dashed arrow within primary cooling body 25. For purposes of the current measurement of the present invention, a fluid (e.g., a liquid, air, or a combination thereof) is channeled through primary cooling body 25 as depicted by the solid arrow leading into the primary cooling channel of primary cooling body 25. As the fluid exits primary cooling body 25, the fluid is channeled through secondary cooling body 24 as depicted by the solid curved arrow leading into the secondary cooling channel of secondary cooling body 24. As the fluid exits secondary cooling body 24, the fluid is either channeled through coil block 23 as depicted by the solid curved arrow leading into the coil cooling channel of coil block 23, or directed away from coil block 23 as depicted by the straight dashed arrow leading away from secondary cooling body 24 whereby additional fluid is channeled through coil block 23 as depicted by the straight dashed arrow leading into the coil cooling channel of coil block 23. The preceding description of the fluid flow through cooling bodies 24 and 25 facilitates a stable current measuring temperature for current sensors 27 (e.g., 22°C), in particular by the mounting of the dissipation elements 28 over current sensors 27. As a result, the current amplifying circuits are capable of measuring current flowing through the electric coils as will be further described herein in connection with FIG. 5.

FIG. 2 illustrates an alternative 20' of coil actuator 20 wherein amplifiers 28 are mounted on secondary cooling body 24, which in turn is mounted on primary cooling body 25. Nonetheless, the operation of alternative coil actuator 20' operates in the same manner as coil actuator 20. FIG. 5 illustrates a current amplifying circuit of the present invention employing a setpoint stage 40, an error amplification stage 50, a dual proportional integral ("PI ² ") stage 60, a pulse-width modulation ("PWM") amplification stage 80, a halve bridge end stage 100, a current measurement stage 130, an overcurrent protection stage 140, a error status stage 150, a power status stage 160 and a temperature status stage 170. Setpoint stage 40 includes a digital-to-analog converter 41 that applies a digital setpoint signal DS to stage 50 whenever a switch 42 is closed and a switch 43 is opened via an inverter 44. Setpoint stage 40 further applies an analog setpoint signal AS to stage 50 whenever switch 42 is opened and a switch 43 is closed via inverter 44.

Error amplification stage 50 includes an illustrated arrangement of an operational amplifier 51, a resistor 52 (e.g., 2k ohms), a resistor 53 (e.g., 20k ohms), a resistor 54 (e.g., 2k ohms) and a negative feedback resistor 55 (e.g., 20k ohms).

PI ² stage 60 includes an illustrated arrangement of a resistor 61 (e.g., 200k ohms), a resistor 62 (e.g., 4M ohms), a capacitor 63 (e.g., 1 nano farads), a resistor 64 (e.g., 200k ohms), an operational amplifier 65, a resistor 66 (e.g., 20k ohms), a resistor 67 (e.g., 4M ohms), a capacitor 68 (e.g., 0.5 nanofarads), a resistor 69 (e.g., 200k ohms) and an operational amplifier 70.

PWM amplification stage 80 includes an illustrated arrangement of a resistor 81 (e.g., 2k ohms), a resistor 82 (e.g., 100k ohms), a resistor 83 (e.g., 10k ohms), a SAW generator 84, a resistor 85 (e.g., 10k ohms), an operational amplifier 86, a voltage source 87, a resistor 88 (e.g., Ik ohm), a transistor switch 89, a transistor switch 90 and a resistor 91 (e.g., Ik ohms).

Half-bridge endstage 100 includes an illustrated arrangement of a voltage source 101 (e.g., 200 volts), a power FET 102, a diode 103, a resistor 104 (e.g., 0.04 ohms) , an inductor 105, a resistor 106 (e.g., 0.04 ohms), a power FET 107, a diode 108, a voltage source 109 (e.g., -200 volts), a capacitor 110 (e.g., 2 microfarads), resistor 111 (e.g., 0.1 ohms) and a temperature sensing resistor 112. Components of endstage 100 temperature controlled by a secondary cooling body of the present invention are highlighted within the dashed boxes 124.

Current measurement stage 130 includes an accurate (lOppm) shunt resistor current sensor 131, which is temperature controlled by a primary cooling body of the present invention as highlighted by the dashed box 125.

Over current protection stage 140 includes an illustrated arrangement of a voltage source 141, a resistor 142, and a comparator 144 connected to stage 100 and a voltage source 143 to thereby generate status over current signal SOC.

Error status stage 150 includes an illustrated arrangement of a resistor 151 connected to a voltage source 180, and a comparator 152 connected to stage 50 and a voltage source 153 to thereby generate a status error signal SE. Power status stage 160 includes an illustrated arrangement of a resistor 161 connected to voltage source 180, and a comparator 162 connected to a power signal PS and a voltage source 163 to thereby generate a status power signal SP.

Temperature status stage 170 includes an illustrated arrangement of a resistor 171 connected to voltage source 180, and a comparator 72 connected to a temperature sensing resistor 112 and a voltage source 173 to thereby generate a status temperature signal ST.

The current amplifying circuit of FIG. 5 has two modes of operation upon being connected to an electric coil via a high coil connection 120 and a low coil connection 121. The first mode is a K-factor measuring mode involving a closing of switch 42, an opening of switch 43 and a enabling of PWM amplification stage 80. A current setpoint of zero via digital setpoint DS is applied to stage 80 whereby a commutation current Ic equals zero and an electro motive force voltage V _EMF is measured and used to calculate the K-factor of the electric coil as would be appreciated by those having ordinary skill in the art. The second mode is a current measuring mode involving an opening of switch

42, a closing of switch 43 and enabling of PWM amplification stage 80. A current setpoint as needed via analog setpoint AS is applied to PWM amplification stage 80 whereby stage 80 controls a flow of commutation current Ic through the electric coil to move a magnetic displacement device interacting with the electric coil as needed. Current sensor 131 provides a current sense IS feedback to error amplification stage 50 indicative of the flow of current through the electric coil whereby the stable current measuring temperature of current sensor 131 facilitates an accurate current sensing by current sensor 131 and thus an accurate movement of the displacement device.

Alternatively for the second mode, switch 42 is closed and switch 43 is opened with the current setpoint being set via digital setpoint DS.

The current amplifying circuit may operate with 150 kHz switching frequency and direct PWM with 30 kHz low-pass filtering within the illustrated compact design. Referring to FIG. 1-5, those having ordinary skill in the art will appreciate an inverted planar motor of the present invention can be utilized in numerous applications, such as, for example, in semiconductor manufacturing applications (e.g., ASML, LAK-Tencor, AMAT, NXP), sample/substrate positioning in reactive or aggressive applications, high acceleration/velocity applications, vacuum applications, production applications, medical applications (e.g., shutter blades in X-ray devices) and consumer electronic applications (e.g., CD/DVD/Blu-Ray drive systems).

Additionally, in practice, the actual structural configuration and relative dimensioning of each component of an inverted planar motor of the present invention is dependent upon the specifics of an explicit application of the motor. Thus, the present invention does not contemplate any particular type of best structural configuration and relative dimensioning of each component of an inverted planar motor of the present invention among the numerous potential applications.

Nonetheless, a temperature for liquid channeling through the primary cooling body may be very stable (e.g., ±0.1 ⁰ C), a temperature for liquid channeling through secondary cooling body may be less stable (e.g., ±1.0°C), and liquid channeling through the coil block may be returned to the primary cooling body.

Further, the cooling bodies 24 and 25 are composed of thermal conductive material, such as, for example, aluminum, ceramics, stainless steel and copper.

Additionally, specifications for the current amplifying circuit may be (1) a supply voltage of +/- 150-200 volts, (2) a maximum current of 20 amps, (3) a bandwidth of 10 kHz, (4) an output impedance 10-500Hz of greater than 50 kω, (5) an amplifier noise below 1 kHz of less than 200 uA rms, (6) an amplifier offset of less than 1 mA, (7) an amplifier gain accuracy of less than 0.3%, (8) a nominal load resistance of 5ω, and a nominal load inductance of 10 mH. While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.