Application Note 5107

Transcription

1 Integration of AEAS-7000 with AEAT-84AD: Mechanical Design Considerations Application Note 5107 Introduction The application note is intended to provide a mechanical design overview on integrating Avago s AEAS-7000 and AEAT-84AD into a multiturn absolute encoder. The integrated multiturn absolute encoder is capable of providing maximal 0-bit or 2 0 unique positions. This also means that it can provide true absolute positional information at 16-bit resolution within one revolution across 1684 shaft turns. Functional Description The AEAS-7000 is a single-turn absolute encoder module in modular form; while AEAT-84AD is a multiturn absolute encoder module without built-in controller. Figure 1 shows the functional block diagram of the integration. The AEAS-7000 is able to provide up to 16-bit resolution with true 6556 unique positional information within one revolution without shaft movement immediately upon power-up. It consists of a low inertial plastic codewheel, with Gray-coded pattern, and an absolute encoder readhead, integrated with highly collimated illumination system and an array of photodetectors. The AEAT-84AD is used to detect numbers of shaft revolution, by providing multiplexed outputs to the controller. As unique-coded gear-wheels techniques are implemented, the combined output through the controller, together with AEAS-7000 MSB, will generate unambigous positional information. Controllers like DSP, FPGA, PLA etc., can be used as the controller for such integration dependent on the design requirement. In this application note, MUIC is used for the controller as it cuts short the development time. Figure 2 illustrates the application example using MUIC with AEAS-7000 and AEAT-84AD. Details on the the availability of this controller is within the multiturn absolute encoder module datasheets in Avago website. An add-on printed circuit board (PCB) interfaces the AEAS-7000 and AEAT-84AD. The controller, in this case - MUIC, seats on the printed circuit board, providing final output from encoding signals of AEAS and AEAT-84AD. Other constituent components are equally important in ensuring final performance of the assembled devices. In general, they are: Encoder shaft or hub Pinion Module 0., 14 teeth Bearing stage Multiturn Module standoff Add-on PCB standoff Connectivity for external use Enclosure Encoder shaft or hub provides a transmission medium between motor shaft movement to the encoder systems, allowing positional information to be encoded. Design, precision and torsional stiffness of the shaft or hub will govern the performance of the final product. Please contact the regional support or factory for further details.

2 This pinion is part of the transmission medium. It is attached at the other end, where AEAT-84AD is located, allowing detection of mechanical revolution through coupling of pinion to first gear wheel within the AEAT- 84AD. Bearing stage serves a mechanical housing for the rest of the components. It also houses bearings, in which shaft or hub is seated. Besides that, the exterior of the bearing stage provides mounting or interface mean to the end user; while the interior of the bearing stage houses the absolute encoder components. The standoffs, whether they are for multiturn module or add-on PCB, elevate the supported components at required heights. Add-on PCB provides an interface medium for AEAS- 7000, AEAT-84AD and controller (MUIC). The physical outline and the layout of the PCB is dependent of the design requirements of the final assembly. For example, the electronic circuit design affects the space requirement of the PCB. The location and design of the standoffs affects the outline of the PCB. The connectivity for external use can be of wires in form of shielded cable, industrial connector, pin header, etc. The choice of connectivity will affect the design of other components, especially add-on PCB and the enclosure design. Component Description The assembly of multiturn absolute encoder comprises the following components, as illustrated in Figure 4. They are as follows: 1. Single turn absolute encoder module AEAS-7000, namely readhead (1a) and code wheel (1b) 2. Multiturn absolute encoder module AEAT-84AD. Controller - MUIC 4. Encoder shaft or hub 5. Pinion Module 0., 14 teeth 6. Bearing stage 7. Multiturn module standoff 8. Add-on PCB standoff 9. Connectivity for external use. Figure shows the final assembly of the multiturn absolute encoder, without the enclosure and final connectivity. For further information on all of the components, please refer to factory. Mechanical Design Considerations The AEAT-84AD is designed to be integrated to AEAS- 7000, via an interface board, which seats the controller (MUIC). This enables design flexibility to cater to different design requirements of the end user. Enclosure provides ingress protection for the components inside the final assembly. It also provides termination for the connector or cable. MULTITURN ABSOLUTE ENCODER Positional Changes within One Revolution AEAS-7000 Data Outputs Mechanical Linkage from End Application to Encoder Systems Number of Revolution Detection AEAT-84AD Controller - MUIC Control Inputs Host Controller Figure 1. Functional block diagram. 2

3 BIT SETTINGS ARE APPLICATION SPECIFIC VCC +5 V 5 V REGULATOR +5 V VB+ VB+ AEAx-84AD MT-CONFIG. 14/16 +2FF CODE MT-ST CR n 100 n +2.5 V LM17L V OUT V IN V REG GND VB- VB- VCC MTMUX x 1 K MTMUX(2:0) CFG N2L16 SRADD2 GRAY MTDIR VDDI GND VDDa 100 n 470R 100 n 470R DRIVER MTDAT GND DOUT SCL NSL DIN MSBINV AEAx-7x00 x 100 K MTDAT(2:0) N2DOUT N2SCL N2NSL N2DIN N2MSBINV DCLK CLKQ HCLK CLOCK OSCILLATOR EXAMPLES LTC1799-SOT2-5 SINGLEGATE RESONATOR 1 2 VDD GND RSET OUT DIV K (10 MHz) MHz /6 HC14 MHz..16 MU-IC1 PRESC (:0) MFFREQ (1:0) HCLK/ H/1/8/64 /2..6 FFOUT STROBE SRCLK MSBINV MFTIME (5:0) MCLR BIT SETTINGS ARE APPLICATION SPECIFIC 1/6 HC14 10 K 2x 1/8 HC14 2x 1/8 HC14 RESET CIRCUIT EXAMPLE IN DE OPTOCOUPLER OUT CR-INPUT OUT OUT+ OUT- IN+ IN- IN DATA+ DATA- CLK+ CLK- CR SERIAL INTERFACE RESET TIME SHOULD BE RELATED TO OSCILLATOR STARTUP TIME Figure 2. Application example of integration of single-turn absolute encoder module and multiturn module using MUIC.

4 Figure. Assembly of multiturn absolute encoder. 1a 1b REF. SURFACE A 6 4 7a 7b Figure 4. Exploded view of multiturn absolute encoder assembly. 4

5 Package Dimensions AEAT-84AD 5.4 ± ± ± ± ± 0.1 R.1 at 6 PLCS 14.0 ± ± ± ± ± ± 0.1 at 6 PLCS 9.5 ± Figure 5. Package dimensions of multiturn absolute module AEAT-84AD. Package Dimensions AEAS (2x) 56 READHEAD CODE DISC 8.02 H6 2x mm PITCH PIN HEADER (Z GAP BETWEEN CODE DISC AND RETICLE) ± Figure 6. Package dimensions of single turn absolute module AEAS

6 The recommended height of AEAT-84AD is typically at 25.6 mm, from Ref. Surface A. The add-on PCB can rest on top of the AEAS-7000 readhead, with the standoff effective length at typically at 19 mm. The multiturn module standoffs design is as shown in Figure 7. The guide standoffs refrain the rotational movement along the shaft axis, while guiding the multiturn module in X-Y position at plane parallel to Ref. Surface A at pre-defined height. Shaft or hub specification is as recommended in the AEAS-7000 datasheet. (See Application Note 5048 for more details.) Mounting distance of codewheel is crucial as it will impact the Z-gap between the codewheel to the AEAS readhead. The AEAS-7000 mounting recommendation is as indicated in Figure 6. (See Application Note 5048 for more details.) Pinion is of module 0. and 14 teeth. The length is recommended to be 4.5 mm as illustrated in Figure 8. The standoffs are for mounting of M2.5 or smaller cap screws to hold the multiturn module in place STAND-OFF 5.0 GUIDE STAND-OFF Figure 7. Multiturn module standoffs design A-.65 Figure 8. Pinion length, codewheel distance from Ref. Surface A, and inner shaft length. 6

7 Assembly Considerations The assembly procedure of multiturn absolute encoder is as follows: 1. First, bearing stage is installed with bearings 2. Shaft is assembled later. All standoffs are installed 4. Single turn encoder module is assembled and aligned, by attaching the code wheel first and then the readhead 5. Add-on PCB is attached and soldered to the single turn encoder module and tightened through cap screws to the add-on PCB standoffs 6. Attach the pinion onto the shaft 7. Insert the multiturn module in place ensure proper mating of connectivity to add-on PCB, proper meshing of pinion to first gear wheel of multiturn module, and proper seating onto/into the multiturn module standoffs 8. Tighten the cap screw to secure the multiturn module to the standoffs 9. Establish the connectivity for external use 10. Unplug the plastic plug as illustrated in Figure 9, before rotating the shaft 11. Place in the enclosure For further information on all the above mentioned assembly procedure, please refer to factory. PLASTIC PLUG IS REMOVED UPON INTEGRATION WITH GEARWHEEL. ZERO POSITION OF COUPLING WHEEL PLASTIC PLUG PINION, MODULE 0., 14 TEETH Figure 9. Mechanical coupling with multiturn encoder module. 7

8 For product information and a complete list of distributors, please go to our website: Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies Limited in the United States and other countries. Data subject to change. Copyright 2006 Avago Technologies Pte. All rights reserved. Obsoletes EN AV01-015EN July 14, 2006