PATENTED SENSOR TECHNOLOGY

DEVELOPED & DESIGNED

IN SWEDEN

What are the benefits?

Simplex Motion offers a motion control sensor for servo motors providing reduced size, weight, and cost, and longer life cycle of the servo motor. This is enabled by replacing the encoder (which is used in conventional servo motors) with Simplex Motion’s patented sensor solution. Further, by combining the sensor solution with an outer rotor motor, Simplex Motion can offer an integrated servo motor with a high torque in relation to its weight and volume.

The benefits of Simplex Motion products are perceived on four levels:

1. It is possible to use a smaller servo motor while maintaining the torque
2. The need of using a gearbox to achieve a certain torque is reduced
3. The energy consumption is reduced due to
   – Removed gearbox (if removed)
   – High efficiency motor type
   See more details under the Energy tab.
4. The precision is increased due to
   – Removed gearbox (if removed)
   – The gearbox (if used) will have a lower ratio (since the motor torque is higher)

Many applications today utilize step motors, since they are very affordable and easy to use. The Simplex Motion concept makes it possible to use a servo motor with almost the same cost level, but as easy to use and with much higher performance.

The general servo motor system uses a motor and a position encoder to measure the true position. The driver controller compares the actual position with the target position and controls the motor torque to minimize this difference, thus closing the control loop. This allows the motor to consume power only when necessary and error conditions such as tool/work piece collisions can be detected and cause the machine to stop.

Some of the following comparisons can be made:

• Simplex Motion servo motor use the patented sensor technology which exclude the external positioning encoder. This makes the system very robust and gives the high accuracy position at all the time. Step motors are used in an open loop fashion, there is no position feedback. This means that if the step motor loses some steps it will have a position error for the remainder of the working session.

•Simplex Motion servomotor has a high speed and the torque is constant over the full range. Step motor have a large holding torque, but the torque falls off quickly as the rotational speed is increased. This makes it difficult to attain high speeds with maintained torque.

•Simplex Motion servo motor is energy efficient, up to 10 times more than Step motors. The Step motor consumes lots of electrical power and get quite hot, since they need continuous current to maintain torque.

•The Step motors are fairly heavy and large compared to servo motors.

Developments in the field of electrical motors and power electronics now push more applications into using brushless DC motors for their improved performance and lifetime. But the electronic commutation of these motors require more electronics and more cables between the motor and its controller.

By putting the control electronics and the motor into the same housing we get an integrated motor drive unit. This simplifies a lot, and there is a rapidly growing number of such products on the market.

There is also a trend towards decentralized motion control, where more control functions and intelligence is moved closer to the motor itself. The SimplexMotion concept follows this trend by having the entire controller in the same housing as the motor.

New global government regulations and laws mandating higher efficiency and lower carbon emissions sharpens the demands on type of motors to use. The Simplex Motion patented sensor technology and motion control makes it possible to use the latest high torque density motors with high efficiency and low cost.

One of the more apparent advantages with an integrated motor drive unit is the simplified installation and wiring. For standalone operation the only wires to the motor is the DC powersupply, and possibly buttons and/or potentiometers directly connected to the motor unit for control purposes.

For external control (and configuration) a communication bus is used. Our models feature a full speed USB connection to make it very easy to control and configure the motor directly from a PC computer.
For more robust industrial environments, or when several units need to be connected to the same bus, there is also support for a Modbus RTU interface. The physical layer uses the RS485 interface, which is readily available on many PLC units and computers. It is a serial bus that needs only 3 wires and is very robust to noise and allows cable lengths up to 1.2km (depending on data speed). Up to 32 devices can be connected to the same bus and controlled from the same host computer. There are low cost RS485 to USB converters that makes it easy to connect the unit to a PC computer (one source is www.ebay.com).

Future products may also include support for the CAN bus, another robust and increasingly popular bus in industrial control applications. This would also include support for the CANopen standard CiA-301/402.

There is also a PC software available for testing and configuring the motor drive unit, as well as API libraries for writing custom software to control the SimplexMotion devices. The API library will support Windows .NET, Labview and Linux development environments.

Environmental problems addressed

The global industry accounts for about 42% of world electricity consumption and 2/3 of it is used to drive electrical motors. If this can be reduced by just a few percent, it can make a big difference in consumption. This section will focus on the energy benefits of SimplexMotions servomotor solution, with its sensor solution and the technical design, compared to other solutions available on the market.

Manufacturers of small motors in Europe and USA are required to comply with more stringent energy conservation standard for small electric motors from 2015. Regulations aimed at boosting energy efficiency and reducing carbon emissions will become more and more stringent and at the same time cover all kinds of motor solutions globally. The Permanent Magnet Synchronous Motor’, or PMSM motors are almost the only technology currently available that meets the requirements. With a high output torque it is in many applications possible to use less mechanical gearing and further decrease losses. And a high dynamic power capability makes it possible to downsize the motor for typical accelerate/move/decelerate motion applications.

The electrification trend is to replace pneumatic systems. This will have the largest impact on energy savings. Simplex Motion servomotors are very well suited for this kind of applications.

Another application that has a large power saving potential is the replacement of step motors. These are common in cost sensitive applications with less performance requirements. Step motors are operated in open loop fashion requiring constant motor current even when standing still. The Simplex Motion concept has the potential to replace step motors in many applications and would incur a large improvement in performance and a huge saving in energy spent.

Simplex Motions servo solution is a high power, high accuracy, cost efficient and low weight motor system with many benefits. A summary of the many benefits and energy savings from using a Simplex Motion servomotor can be seen in this bulleted list below.

Addressable market assumed is 10% of the total number of all motors in the range 10-750W, which is 200 million motors. Of this addressable market the assumption is based on a market penetration of 0,5% = 1 000 000 motors to get a realistic base for the calculations made. ^[1]

The benefits and savings are;

• Downsizing gearboxes
  • Energy savings from 3% to 50% depending on type of gearbox
  • Potential energy savings of 12,5 GWh based on a 3% saving per gearbox (equivalent to the yearly consumption of 2 500 households).
  • Lower material consumption, i.e. a more sustainable solution
• Replace brushed motors
  • Energy savings from 11-67%
  • Potential to speed up technology shift
    • Less maintenance
    • Less energy consumption
    • Longer lifetime of products
• Replace step motors
  • Energy savings from 40% to over 90%
  • Potential energy savings of 860GWh (equivalent to the yearly consumptions of 172 000 households).
• Replace other integrated servomotors
  • Factor 3 higher peak torque per weight
  • Less parts
  • Lower material consumption, i.e. a more sustainable solution
  • Saves energy for moving systems because of low weight, robot arms for example.
• Replace pneumatic systems
  • Energy savings 71%
  • Potential yearly energy savings of 5.7 TWh (equivalent to the yearly consumptions of 1.1 million households)
• Potential to use SimplexMotion technology platform on large motors (example Transversal Flux Machine) for direct drive applications
  • Energy savings 17%

There are several advantages with the SimplexMotion solution; the high torque minimizes the need to use gearboxes that both lower the power consumption and saves environment by using less material. The patented sensor technology drives down the cost of the system and makes SimplexMotion competitive against the other servomotor and stepper motor manufacturers. These things combined makes the SimplexMotion patented sensor solution and servomotor design a strong competitor both in energy consumption and performance.

[1] https://www.iea.org/publications/freepublications/publication/EE_for_ElectricSystems.pdf [2017-01-27]

The electronics within the integrated motor drive unit is compact and built using the latest and most cost efficient components. There has been a remarkable development of high power mosfet transistors, and also on digital signal processors suitable for advanced motor control. These key components has been chosen with great care to maximize the performance / cost ratio. The implemented motor control uses space vector modulation techniques in combination with field-oriented control algorithms (sometimes called vector control) to maximize performance and efficiency. On a higher level a PID control algorithm is used for closed loop control of speed, position and torque.

The electronics has been designed to match the long lifespan of the brushless DC motor by using only components that can tolerate elevated temperatures and harsh environments. Protection features monitor motor temperature, supply voltage, motor torque and motor current to prolong life of the product.

Electromagnetic compatibility issues are virtually eliminated by having the motor cables extremely short and within the housing. The typical noise emissions from long motor cables with high frequency switching noise is no longer an issue. Nor is the switching noise cross coupled to position encoder signals a problem anymore. The only type of noise emission that still poses a problem is conducted noise on the power supply cables.

The SimplexMotion products has an internal high order filter to limit the noise above 150kHz to levels below the stated limits in EN61800-3. There are no electrolytic capacitors in this filter since those components have a limited lifespan. Spread spectrum techniques are utilized to minimize cost to achieve this. The products have been EMC tested and are CE-marked.

The motor type that is used in the SimplexMotion range of integrated motor drives is a brushless DC motor with sinusoidal back EMF. This type of motor is often called ‘Permanent Magnet Synchronous Motor’, or PMSM for short, and is commonly used as servo motors. The SimplexMotion products utilize an outer rotor version of this motor type. This means that the motor has the stationary part (the stator) in the central position, while the rotating part (the rotor) is on the outside and encloses the stator. Since todays advanced materials allow the permanent magnets to be both very strong and small, it is possible to make the rotor thin and this allows the air gap between the stator core and the rotor magnets to have a large diameter. A large diameter of the air gap results in a high motor torque. The large volume inside the air gap allows a lot of copper in the windings, which minimizes conduction losses and allows the motor efficiency to be high.

But there are also drawbacks to an outer rotor motor. The larger diameter of the rotor increases the moment of inertia, which is especially harmful for fast dynamic positioning applications. But this effect is to a large degree compensated by the higher motor torque. Especially after considering the added moment of inertia of the application load the mechanical time constant (The ratio of torque to moment of inertia) is often advantageous for the outer rotor configuration.

Another drawback is the more difficult cooling of the motor windings. Having the windings in the center of the motor requires a more careful design of thermal issues. But by using both radiation, convection and conduction mechanisms for heat removal makes it possible to obtain a high ratio of power to weight of the final system. In the SimplexMotion concept there is also a thermal monitoring of the motor and the electronics to provide warnings or motor shutdown in case of over temperature.

The motors used are available from established manufacturers in many different sizes to allow rapid development of integrated motor drive products.

To allow closed loop position control there must be a motor position feedback sensor. Most common today are optical quadrature encoders. But for precise control of brushless DC motors there is also need for an absolute position sensor to determine timing for motor winding commutation. This is most often done with digital magnetic hall sensors placed inside the motor.

Having two sensor systems in parallel increase cost and an important step towards a cost optimized design would be a sensor system that can perform both functions.

The sensor system used on the SimplexMotion products is a novel approach that realizes this with a cost that is lower than the optical encoder alone.

The position sensor utilizes the leakage magnetic field from the rotor of the motor to sense position. Two linear hall effect sensors are placed on the same circuit board as the rest of the electronics in the integrated motor drive unit. The sensor technology is patented.

The design of the housing and assembly of the unit is important for thermal issues and to keep cost down. In the SimplexMotion products the housing also serves as a heatsink for both the motor and the electronics. The main housing is fabricated from an extruded aluminum profile. It is black anodized to optimize the thermal performance. There is only one circuit board within the unit and a minimum of cabling.

The housing allows two ways of mounting the unit in its application environment. Either by using metric M4 screws in the front panel, or by using square nuts in two slots on the units bottom side.