5. Passive Micromechanical Elements

The passive micromechanical elements available in the Parameterized Micromechanical Element library are described in this chapter. Again, there are two versions of most elements implemented on each of the first and second structural layers. In some cases, like bearing2, the element is designed to mechanically interface with a rotary element on structural layer 2 and consists of structures on both structural layers. The geometrical parameters passed to the generators use 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 passive elements are currently available in the CaMEL PME library:


Table of Contents


5.1 Journal Bearing Element: bearing1

The bearing1 PME generator generates a journal bearing intended to connect with a rotary element on the first structural layer. The shaft anchored to the substrate, and the retaining cap on top of the shaft central to the bearing are formed on the second structural layer. The design parameters are:

  rcap:    radius of cap on central shaft, �m
  rinner:  inner radius of journal rotor, �m
  router:  outer radius of journal rotor, �m
  name:    name of cell.

The outside of the shaft on structural layer 2 is one bearing surface while the inside of the rotor on structural layer 1 is the second bearing surface. The clearance between the two bearing surfaces is determined by the thickness of the second sacrificial layer used in the surface micromachining fabrication process. The radius of the shaft is set by the inner radius of the journal rotor and the second sacrificial layer thickness used in the process. The origin of the cell is located at the center of the shaft and cap.

Element calling sequence:

PME bearing1(double rcap, double rinner, double router, char *name)

Figure 15. Layout and cross section of bearing1 journal bearing. The cross section illustrates how the spacing between the shaft and rotor is determined by the second sacrificial layer. The substrate is not shown in the cross section; the layers shown are: first sacrificial layer, first structural layer, second sacrificial layer, and second structural layer.

5.2 Journal Bearing Element: bearing2

The bearing2 PME element generates a journal bearing intended to connect with a rotary element on structural layer 2. The design parameters are:

  rcap:    radius of cap on central shaft, �m
  rinner:  inner radius of journal rotor, �m
  router:  outer radius of journal rotor, �m
  name:    name of cell.

The outside of the shaft on structural layer 2 is one bearing surface while the inside of the rotor on structural layer 1 is the second bearing surface. The clearance between the two bearing surfaces is determined by the thickness of the second sacrificial layer. The radius of the shaft is set by the inner radius of the journal rotor and the second sacrificial layer thickness used in the process. The rotor has an outer ring on structural layer 2 that is mechanically connected to the rotary part of the bearing on structural layer 1. The origin of the cell is located at the center of the shaft and cap.

Element calling sequence:

PME bearing2(double rcap, double rinner, double router, char *name)

Figure 16. Layout and cross-section of bearing2 rotary bearing element. It is similar to a bearing1 element but has bushings and an additional ring on structural layer 2.

5.3 Linear Crab Leg Suspension Elements: lcls1, lcls2

The lcls1 and lcls2 routines generate linear crab leg suspensions on structural layer 1 and structural layer 2, respectively. The design parameters used are:

  lbeam1:    length of beam1, �m
  wbeam1:    width of beam 1, �m
  lbeam2:    length of beam 2, �m
  wbeam2:    width of beam 2, �m
  beam1sep:  separation between type 1 beams, �m
  swidth:    width of shuttle width, �m
  slength:   length of shuttle, �m
  wanchor:   width of anchor support, �m
  wsyoke:    width of shuttle yoke, �m
  lsyoke:    length of shuttle yoke, �m
  name:      name of cell.

The geometry of the element is illustrated in Figure 17. The local origin of the element is at the center of the shuttle mass. Actuators can be connected to the yokes on the shuttle mass.

Element calling sequence:

PME lcls1(double lbeam1, double wbeam1, double lbeam2, double wbeam2,
          double beam1sep, double swidth, double slength,
          double wanchor, double wsyoke, double lsyoke, char *name)
PME lcls2(double lbeam1, double wbeam1, double lbeam2, double wbeam2,
          double beam1sep, double swidth, double slength,
          double wanchor, double wsyoke, double lsyoke, char *name)

Figure 17. Linear crab leg suspension element. The origin of the cell is located at the center of the shuttle mass. Linear actuation elements can be connected to the shuttle yokes to create a linear resonator.

5.4 Linear Crab Leg Suspension Elements: lcls1b, lcls2b

The lcls1b and lcls2b routines generate linear crab leg suspensions on structural layer 1 and structural layer 2, respectively. The design parameters used are:

  lbeam1:    length of beam 1, �m
  wbeam1:    width of beam 1, �m
  lbeam2:    length of beam 2, �m
  wbeam2:    width of beam 2, �m
  beam1sep:  separation between type 1 beams, �m
  swidth:    width of shuttle width, �m
  slength:   length of shuttle, �m
  wanchor:   width of anchor support, �m
  wsyoke:    width of shuttle yoke, �m
  lsyoke:    length of shuttle yoke, �m
  name:      name of cell.

The geometry of the element is illustrated in Figure 18. The local origin of the element is at the center of the shuttle mass. Actuators can be connected to the yokes on the shuttle mass.

Element calling sequence:

PME lcls1b(double lbeam1, double wbeam1, double lbeam2,
           double wbeam2, double beam1sep, double swidth,
           double slength, double wanchor, double wsyoke,
           double lsyoke, char *name)
PME lcls2b(double lbeam1, double wbeam1, double lbeam2,
           double wbeam2, double beam1sep, double swidth,
           double slength, double wanchor, double wsyoke,
           double lsyoke, char *name)

Figure 18. Design parameters for the linear crab leg suspensions lcls1b and lcls2b. The origin of the cell is at the center of the shuttle mass and drive elements should be connected to the yokes on the shuttle.

5.5 Linear Folded Beam Suspension Elements: lfbs1, lfbs2

The lfbs1 and lfbs2 routines generate linear folded beam suspensions on structural layer 1 and structural layer 2, respectively. The element parameters used are:

  lbeam:    length of beam, �m
  wbeam:    width of beam, �m
  beamsep:  separation between beams, �m
  wbar:     width of connecting bar, �m
  swidth:   width of shuttle width, �m
  wanchor:  width of anchor support, �m
  wsyoke:   width of shuttle yoke, �m
  lsyoke:   length of shuttle yoke, �m
  name:     name of cell.

The geometry of the element is illustrated in Figure 19. The local origin of the element is at the center of the shuttle mass. Actuators or other mechanical elements can be connected to the yokes at the ends of the shuttle mass.

Element calling sequence:

PME lfbs1(double lbeam, double wbeam, double beamsep, double wbar,
          double swidth, double wanchor, double wsyoke, double lsyoke,
          char *name)
PME lfbs2(double lbeam, double wbeam, double beamsep, double wbar,
          double swidth, double wanchor, double wsyoke, double lsyoke,
          char *name)

Figure 19. Salient features of the linear folded beam suspension generated by lfbs1 and lfbs2. The origin of the cell is located at the center of the shuttle mass. Drive elements should be fixed to the yokes at either end of the shuttle.

5.6 Dual Archimedean Spiral Spring: spiral1, spiral2

The spiral1 and spiral2 routines generate dual Archimedean spiral springs on structural layer 1 and structural layer 2, respectively. A possible application of the spiral spring is in a torsional suspension system. The element parameters used are:

  rshaft:  radius of support shaft, �m
  rinner:  starting radius of spiral beam, �m
  router:  final radius of spiral beam, �m
  length:  length of each spiral beam, �m
  width:   width of the spiral beam, �m
  rrotor:  outer radius of rotor support, �m
  name:    name of cell.

The geometry of the element is illustrated in Figure 20. The local origin of the element is at the center of the shaft. Actuators or other mechanical elements can be connected to the rotor supports at the ends of the spiral spring. Parameters such as rinner, router, and length apply to the central axis of the spiral beam.

Element calling sequence:

PME spiral1(double rshaft, double rinner, double router,
            double length, double width, double rrotor, char *name)
PME spiral2(double rshaft, double rinner, double router,
            double length, double width, double rrotor, char *name)

Figure 20. Dual Archimedean spiral spring element. The length parameter of the spiral beam corresponds to the length of the central axis of the beam. The central support shaft is anchored to the substrate.