ECT 459 Lecture 8 Encoder Feedback

Linear Linear –Absolute –Incremental –Both Rotary Rotary –Absolute –Incremental –Both

Encoder Feedback Resolutions Resolutions –2 …. 32,768 cpr (absolute) –2 … 5 million cpr (incremental) Interfaces Interfaces –Push-Pull, Open Collector, TTL Power Power –5, 8, 10, …..24, 30 VDC Output Code Formats Output Code Formats –Gray –Gray Excess –Binary –Binary Coded Decimal

Encoder Feedback Interfaces Interfaces –DeviceNet –CanOpen –Profibus –SSI Heads Heads – Mechanical – Optical – Magnetic Turns Turns –Single –Multi

Encoder Feedback Shaft Sizes Shaft Sizes –Various –Hollow shaft –Single or Double-ended Applications Applications –Automatic Storage and Retrieval –Valve Controls –Robotics

Encoder Feedback Sensor Arrays Sensor Arrays – –The SinCos® pickup system is also different from conventional encoder systems. The sensitive area of the OPTO-ASIC consists of a sophisticated sensor array, where individual sensors are selectively accessible. The sensor array reads complete serial data strings from the barcode track.

Encoder Feedback Code Disk Design Code Disk Design – –The small SinCos® code disk condenses absolute position information into one non- repeating circular barcode pattern. A second track with analog sine/cosine signals is used to enhance resolution and accuracy. Absolute position up to 15-bit is available upon motor start-up, and any time it is requested by the motor drive - such as for synchronization.

Encoder Feedback Single and Multi-Turn Absolute Encoders Single and Multi-Turn Absolute Encoders – –Use single turn encoders when the full range of motion in the application occurs within one full revolution (360°) of the encoder shaft. Multi-turn encoders are recommended for applications involving multiple revolutions of the encoder shaft. In multi- turn encoders, a high precision, miniaturized gear train, with a magnet on each gear stage, is used to mechanically store position information over as many as 4,096 turns. The position of each gear stage is determined with a pair of Hall sensors. This eliminates the need for costly and often unreliable counters and battery back up systems. Also, position changes that occur while the power is off are automatically tracked.

Encoder Feedback

Wire Draw Encoders Wire Draw Encoders –Encoder integrated with string pot up to 1.67 kilometers Wire draw mechanisms are linear-to rotational, industrial motion conversion modules, coupled with encoder feedback, to provide cost-effective linear position measurement solutions that precisely fit your requirements. These systems are housed in rugged industrial enclosures, and contain a stainless steel or thermoplastic composite cable wound on a precise, constant- diameter spool. The cable is attached to the apparatus whose position is being measured, and is extended and retracted as the apparatus moves. A spring on the spool maintains cable tension. Position feedback is provided by a standard incremental or absolute rotary shaft encoder. These position transducers allow very flexible measuring paths, since the cable can be guided around obstacles using pulleys, etc. The heavy-duty enclosure of the encoder and spool housing provide excellent protection against contaminants, shock and other abuses.

Encoder Feedback Linear Magnetic Tape Encoder Linear Magnetic Tape Encoder Consists of a magnetic tape and sensor head. The magnetic tape provides the scale for measuring systems up to 40 meters long. The absolute information is magnetized onto the tape in a 12-bit sequential code. This position information is enhanced by interpolation of sine/cosine signals provided by an additional incremental track that is magnetized on the tape. The magnetic tape is laminated onto a ferromagnetic steel strip which is used both as a magnetic return path and a dimensionally stable mounting aid. The magnetic tape is supplied with an adhesive back for mounting by the user. A non-contact magnetic sensor with integrated electronics is mounted to the apparatus whose position is to be measured. As the sensor moves over the measuring tape, its position is output with a resolution as low as 1 µm over a 16 meter range, or 10 µm over a 40 meter range. Position data is output via real-time compensated SSI (Synchronous Serial Interface), or RS-485. A number of parameters such as offset, resolution and start points can be configured by the user.

Encoder Feedback Custom Programmable Custom Programmable –Incremental encoders by SICK Stegmann empower the customer to freely program the number of lines from 1 to 8,192 and the width of the zero pulse using a USB cable and a simple programming software tool. –