4. Active Micromechanical Elements

This chapter describes the various active micromechanical elements available in the Parameterized Micromechanical Element library. In most cases, there are two versions of the element which are similar except for the structural layer used. Elements using the first structural layer are designated by a 1 in the name of the element, while those on the second structural layer are designated with a 2 in the name. For example, lcomb1 designates a linear comb drive on structural layer 1 while lcomb2 generates a linear comb drive on structural layer 2. The geometrical parameters passed to the generators are in the following units: �m for length dimensions and degrees for angles. For other design parameters, the units used are specified in the description of the element.

The following active elements are currently available in the CaMEL PME library:

The element calling sequence for each generator shows the sequence and data type of arguments required by the element. Variable and function data types shown in bold letters are for information purposes and should be kept in mind if the library functions are called directly from a C program. They do not have to be explicity included in the input file under normal usage by the average user.


Table of Contents


4.1 Harmonic Side Drive Elements: hsdm1, hsdm2

The hsdm1 and hsdm2 routines generate the harmonic side drive actuator on structural layer 1 and structural layer 2, respectively. The following design parameters must be passed to the generator in the order specified:

  rri:     inner rotor radius, �m
  rro:     outer rotor radius, �m
  rwidth:  rotor ring width, �m
  rsi:     stator inner radius, �m
  rso:     stator outer radius, �m
  phisp:   stator pole angle, degrees
  phisg:   angular gap between stator poles, degrees
  name:    name of cell.

The relation between the geometry of the structural layer and the element parameters is illustrated in the accompanying figure. The actuator is generated with its local origin at the center of the stator. A central bearing has to be added to complete the harmonic or wobble motor. All lengths are specified in microns and angles in degrees.

Element calling sequence:

PME hsdm1(double rri, double rro, double rwidth, double rsi,
          double rso, double phisp, double phisg, char *name)
PME hsdm2(double rri, double rro, double rwidth, double rsi,
          double rso, double phisp, double phisg, char *name)

Figure 7. Parameters used to call the harmonic side drive generators hsdm1 and hsdm2. The origin of the element is at the center of the stator and is shown marked with cross hairs.

4.2 Linear Comb Drive Elements: lcomb1, lcomb2

The lcomb1 and lcomb2 elements generate linear comb drives on structural layer 1 and structural layer 2, respectively. The following design parameters must be passed to the generator in the order specified:

  arwidth:   active rotor comb width, �m
  rywidth:   rotor yoke width, �m
  sywidth:   stator yoke width, �m
  flength:   length of comb fingers, �m
  fwidth:    width of comb fingers, �m
  airgap:    air gap between fingers, �m
  rsoverlap: stator-rotor finger overlap, �m
  name:      layout cell name

The relation between the geometry of the structural layer and the element parameters is illustrated in the figure below. The comb is generated with its local origin at the center of the rotor yoke.

Element calling sequence:

PME lcomb1(double arwidth, double rywidth, double sywidth,
           double flength, double fwidth, double airgap,
           double rsoverlap, char *name)
PME lcomb2(double arwidth, double rywidth, double sywidth,
           double flength, double fwidth, double airgap,
           double rsoverlap, char *name)

Figure 8. Definition of geometric parameters passed to the lcomb1 and lcomb2 parameterized elements. The parameters apply to the structural layer of the element. The cross hairs mark the location of the origin of the element.

4.3 Linear Side Drive Elements: lsdm1, lsdm2

The lsdm1 and lsdm2 generators create linear side drive elements on structural layer 1 and structural layer 2, respectively. The parameters required by lsdm1 and lsdm2 are:

  mlength:    active length of motor, �m
  swidth:     stator electrode width, �m
  spitch:     stator electrode pitch, �m
  slength:    stator electrode length, �m
  rwidth:     rotor tooth width, �m
  rpitch:     rotor tooth pitch, �m
  rheight:    rotor tooth height, �m
  yokewidth:  rotor yoke width, �m
  airgap:     air gap between stator and rotor pole faces, �m
  roffset:    rotor offset with respect to the stator, �m
  name:       name of cell

The origin of the element is located at the center of the stator.

Element calling sequence:

PME lsdm1(double mlength, double swidth, double spitch,
          double slength, double rwidth, double rpitch,
          double rheight, double yokewidth, double airgap,
          double roffset, char *name)
PME lsdm2(double mlength, double swidth, double spitch,
          double slength, double rwidth, double rpitch,
          double rheight, double yokewidth, double airgap,
          double roffset, char *name)

Figure 9. Parameters used to call the lsdm1 and lsdm2 elements.

4.4 Unidirectional Rotary Comb Drive Elements: rcombu1, rcombu2

The rcombu1 and rcombu2 elements generate unidirectional rotary comb drives on structural layer 1 and structural layer 2, respectively. The following design parameters must be passed to the generator in the order specified:

  aclength:  active angular comb length, degrees
  rri:       inner radius of rotor, �m
  rsi:       inner radius of stator comb, �m
  rso:       outer radius of stator comb, �m
  rspokew:   rotor spoke width, �m
  sspokew:   stator spoke width, �m
  fwidth:    width of comb fingers, �m
  airgap:    airgap between adjacent comb fingers, �m
  trsovlp:   angular stator-rotor finger overlap, degrees
  name:      layout cell name

The relation between the geometry of the structural layer and the element parameters is illustrated in the figure below. The comb is generated with its local origin at the center of the circular comb fingers and the rotor spoke is aligned with the x-axis.

Element calling sequence;

PME rcombu1(double aclength, double rri, double rsi, double rso,
            double rspokew, double sspokew, double fwidth,
            double airgap, double trsovlp, char *name)
PME rcombu2(double aclength, double rri, double rsi, double rso,
            double rspokew, double sspokew, double fwidth,
            double airgap, double trsovlp, char *name)

Figure 10. Unidirectional comb element rcombu1 or rcombu2. The stator outer radius, rso, is adjusted automatically to accommodate the specified finger widths and gaps. The air gap is the radial distance between adjacent comb fingers.

4.5 Unidirectional Rotary Comb Drive Elements: rcombu1a, rcombu2a

The rcombu1a and rcombu2a elements generate unidirectional rotary comb drives on structural layer 1 and structural layer 2, respectively. The following parameters must be passed to the generator:

  xcenter:   x location of center of circular comb fingers, �m
  ycenter:   y location of center of circular comb fingers, �m
  aclength:  active angular comb length, degrees
  rri:       inner radius of rotor, �m
  rsi:       inner radius of stator comb, �m
  rso:       outer radius of stator comb, �m
  rspokew:   rotor spoke width, �m
  sspokew:   stator spoke width, �m
  fwidth:    width of comb fingers, �m
  airgap:    airgap between adjacent comb fingers, �m
  trsovlp:   angular stator-rotor finger overlap, degrees
  name:      layout cell name

The center of the circular fingers is at (xcenter, ycenter) and the rotor spoke is aligned with the x-axis.

Element calling sequence:

PME rcombu1a(double xcenter, double ycenter, double aclength,
             double rri, double rsi, double rso, double rspokew,
             double sspokew, double fwidth, double airgap,
             double trsovlp, char *name)
PME rcombu2a(double xcenter, double ycenter, double aclength,
             double rri, double rsi, double rso, double rspokew,
             double sspokew, double fwidth, double airgap,
             double trsovlp, char *name)

Figure 11. Parameter definition for unidirectional rotary comb drive rcombu1a and rcombu2a.

4.6 Bidirectional Rotary Comb Drive Elements: rcombd1, rcombd2

The rcombd1 and rcombd2 elements generate bidirectional rotary comb drives on structural layer 1 and structural layer 2, respectively. The following design parameters passed to the generator are:

  aclength:  active angular comb length of each sector, degrees
  rri:       inner radius of rotor, �m
  rsi:       inner radius of stator comb, �m
  rso:       outer radius of stator comb, �m
  rspokew:   rotor spoke width, �m
  sspokew:   stator spoke width, �m
  fwidth:    width of comb fingers, �m
  airgap:    airgap between adjacent comb fingers, �m
  trsovlp:   angular stator-rotor finger overlap, degrees
  name:      layout cell name

The geometry of the structural layer and element parameters are shown below. The comb is generated with its local origin at the center of the circular comb fingers and the rotor spoke is aligned with the x-axis and if necessary, rso is altered to fit the finger width and airgap specified.

Element calling sequence;

PME rcombd1(double aclength, double rri, double rsi, double rso,
            double rspokew, double sspokew, double fwidth,
            double airgap, double trsovlp, char *name)
PME rcombd2(double aclength, double rri, double rsi, double rso,
            double rspokew, double sspokew, double fwidth,
            double airgap, double trsovlp, char *name)

Figure 12. Bidirectional rotary comb drive elements generates two comb segments.

4.7 Rotary Comb Drive Elements: rcdm1, rcdm2

The rcdm1 and rcdm2 elements generate bidirectional rotary comb drives with four sectors on structural layer 1 and structural layer 2, respectively. The following parameters are required:

  rringi:   inner radius of rotor ring, �m
  rringo:   outer radius of rotor ring, �m
  rsi:      inner radius of stator comb, �m
  rso:      outer radius of stator comb, �m
  fwidth:   width of comb fingers, �m
  airgap:   airgap between adjacent comb fingers, �m
  rspokew:  rotor spoke width, �m
  sspokew:  stator spoke width, �m
  sspokeg:  gap between stator spokes at inner stator radius, �m
  rsovlp:   stator-rotor finger overlap as a fraction of angular finger length
  name:     layout cell name

The origin of the cell is located at the center of the rotor ring. The active length of the comb sectors is calculated automatically.

Element calling sequence:

PME rcdm1(double rringi, double rringo, double rsi, double rso,
          double fwidth, double airgap, double rspokew,
          double sspokew, double sspokeg, double rsovlp, char *name)
PME rcdm2(double rringi, double rringo, double rsi, double rso,
          double fwidth, double airgap, double rspokew,
          double sspokew, double sspokeg, double rsovlp, char *name)

Figure 13. Salient features of the rotary comb drive motor element with four segments.

4.8 Rotary Side Drive Elements: rsdm1, rsdm2

The rsdm1 and rsdm2 elements generate bidirectional rotary comb drives with four sectors on structural layer 1 and structural layer 2, respectively. The following parameters are required:

  rring:    inner radius of rotor ring, �m
  rri:      inner radius of rotor tooth, �m
  rro:      outer radius of rotor tooth, �m
  rsi:      inner radius of stator electrode, �m
  rso:      outer radius of stator electrode, �m
  phirp:    angular width of rotor pole (tooth), degrees
  phirg:    angular gap between adjacent rotor teeth, degrees
  phisp:    angular width of stator pole, degrees
  phisg:    angular gap between adjacent stator poles, degrees
  roffset:  angular offset of rotor with repect to stator, degrees
  name:     layout cell name

The origin of the cell is located at the center of the rotor ring. With a roffset of zero, the first rotor tooth will be aligned with the first stator electrodes, i.e., the x-axis.

Element calling sequence:

PME rsdm1(double rring, double rri, double rro, double rsi,
          double rso, double phirp, double phirg, double phisp,
          double phisg, double roffset, char *name)
PME rsdm2(double rring, double rri, double rro, double rsi,
          double rso, double phirp, double phirg, double phisp,
          double phisg, double roffset, char *name)

Figure 14. Salient features of the rotary side drive element on the structural layer.