Linear Encoder Position Sensor
Position Encoders – General
Position sensors (encoders) provide an output signal proportional to the angle – or speed, of rotational – or linear, movement. They are used whenever the motion of a machine element is to be controlled or monitored. Typical applications are in industrial automation, robotics, machine tools, office machines, automotive, etc. In technology, virtually “every thing that moves” involves a position encoder.
Until recently two primary position encoder technologies have been used: magnetic, and optic, introduced in the 1930’s and in the 1950’s, respectively.
Both angular and linear position encoders are of either incremental or absolute. An incremental encoder provides an output, which is relative to the position where power was turned on, therefore, the corresponding machine element must first move to a known reference position – in order to make the reading absolute. Most optical encoders are incremental; they include a glass code-disk, an optical read-head, electronic circuitry, and precision bearings. Magnetic encoders (“Resolvers”) resemble small electric motors – having wire wound rotor and stator, they are of the absolute type and provide the true position instantly upon power turn-on, but with a limited accuracy.
Advantages of the Electric Encoder™
The Electric Encoder™ technology offers a variety of and position sensing devices by combining the advantages of optic and magnetic encoders, i.e., accuracy and absolute output. It also offers several variants, which are impossible to duplicate using magnetic and optic technologies. Both angular and linear Electric Encoder™ boasts the following features:
- Flexible customization options
- Low cost
- Very low profile
- Extremely simple construction
- Very low power consumption
- Very high tolerance to mechanical mounting errors
- Virtually no failure mechanism
- Wide temperature range (-55 to +150 Celsius)
- High mechanical robustness
- Insensitivity to electromagnetic interference
- Insensitivity to moisture conditions
The Electric Encoder™ constitutes a “missing link” in the sense that out of the three fundamental fields: magnetic, electromagnetic (light) and electric, only two have been used for position sensing. The electric field has been ignored due to technical hurdles – except for niche applications.
The Electric Encoder™ technology of using the electric field for position sensing was conceived, developed, and continually refined since 1994. It is proprietary to Netzer Precision (three patents pending) and is not available elsewhere. Although less than 2 years in the market, it has already been adapted to a wide range of applications – see below, demonstrating its superiority and versatility, and refuting all of the assumed disadvantages.
What makes the Electric Encoder™ unique?
The (rotary) Electric Encoder™ comprises two parts; a stator and a rotor. The stator is made of a conventional printed circuit board with electronic components on one side, and a printed geometrical pattern on the other side. The pattern holds part of the secrets of the technology and of its flexibility. Facing the pattern side of the stator is the rotor – which is injection molded from a polymer with special dielectric properties. Unlike in optical encoders the rotor is “holistic”, i.e.; its whole area contributes, at any time, to the output signal. This results in two powerful mechanisms that enhance the performance of the Electric Encoder™:
Geometrical compensation is a result of the rotor symmetry where each two opposing regions react oppositely to rotor motions, such as tilt, decenter, generating opposing effect on the output signals. In combination with the signal insensitivity to rotor axial motion the Electric Encoder™ reacts to pure rotation only – an attribute of an “ideal” rotation encoder. One of the practical outcomes is that no internal ball bearings are needed, since the rotor can be directly mounted on the host shaft and tolerate its inaccuracies.
Averaging – which results from the output signal being contributed by multiple poles. Therefore, any effect due to production tolerance, temperature variations, contamination, etc, tends to average out in proportion to the number of poles (to 64).
The Electric Encoder™ is, therefore, rather counter-intuitive in breaking an unwritten rule, which states: “ High precision measurement requires a precision built sensor”.
The fact that the Electric Encoder™ relies on electric field makes it inherently insensitive to magnetic fields; therefore, it can be installed inside electric motors without magnetic shielding, while an internal shield protects it from external electric fields. The absence of ball bearings, glass disc, light sources and detectors, leaves the Electric Encoder™ with virtually no failure mechanisms, altogether resulting in extreme ruggedness and reliability.
Applications of the Electric Encoder™
- rotary electric encoders are used in robot arms to provide absolute angle. The most lucrative application is for a space vehicle articulated arm.
- Industrial automation. Both rotary and linear Electric Encoders are used in semiconductor handling equipment, packaging equipment, automotive paint sprayers, etc.
- Automotive. Rotary Electric Encoders are being designed into electrically assisted breaking systems, Electrically assisted steering systems, Starter/Alternators, and main traction motors.
- Military. Rotary Electric Encoder is being designed into Tank fire control system. Linear Electric Encoder is bidding for the JSF (Joint Strike Fighter) triple redundancy flap control system.
- Medical. Linear Electric Encoder is being supplied for a CT (computerized Tomography) machine and installed into a prototype cardiac bypass pump. Rotary Electrical Encoder is being evaluated for a teleoperated robotic surgeon.
- Ball bearings. The rotary Electric Encoder has been tested incorporated in a ”smart ball bearing”.
- Miscellaneous: Elevator doors, Fiber optic splicing machines, 3D displays: Fuel reservoir level sensors, SMD assembly machines, Milking machines, etc.
The total world market of rotary and linear encoders is $1.3B (estimate by two independent sources). It includes rotary and linear encoders mostly incremental and partly absolute. Netzer technologies cover the full spectrum of the market and the full spectrum of applications. Currently Netzer encoders are included or designed into applications that range from small electric motors through medical equipment, military equipment, satellite communication antennas, Sun energy collectors to space robots.
The technology is protected by the following granted and pending patents:
ØElectric encoder technology Granted US 6,492,911. Europe EP 1173 730 B1
This patent is also granted in and in Taiwan, and is pending in Japan and China.
ØMulti-speed rotary electric encoder Granted US 6,788,220 pending in Europe Japan and in China.
Ø Linear cabled readhead encoder pending in the US, Europe, China and Japan
Ø Linear cable-free encoder pending in the US, Europe, China and Japan
ØMultiturn encoder: Granted US 6,628,741 pending in Europe, China and Japan.
The company directly employs 15 people including research development, marketing. It has representatives in Europe, North America and Japan.
The company main income comes from several customers in the fields of medical equipment, military, semiconductor, and communication. It faces the situation that the demand from the market exceeds its capabilities. The company seeks an investment of $1~3M which is needed for finishing new standard products, increasing the R&D team and increasing the sales force.