The shift to smart manufacturing leverages advanced technologies to enhance yield, productivity, agility, efficiency, and safety while simultaneously reducing costs.
Intelligent motion control is pivotal in this transformation. It often necessitates updating older factories by replacing fixed-speed motors and controls with superior motion control devices. These devices rely on advanced sensing for precise motion and power control. To achieve optimal workflow and production agility, designers must also implement real-time connectivity between production machinery and manufacturing execution systems.
High-speed network interfaces
Many advanced technologies and system-level solutions are available to enable the migration to intelligent motion control, yet designers are often left on their own to piece the system together.
These include components for isolated current sensing and position feedback for multi-axis control
This situation is changing, with comprehensive solution sets now available to help kickstart a motion control design. These include components for isolated current sensing and position feedback for multi-axis control of a motor’s speed and torque, as well as sensors for machine health monitoring to reduce unplanned downtime. High-speed network interfaces are also included, facilitating data sharing between machines and higher-level control and management networks.
Industrial motion control
This article briefly discusses the importance of improved motor control. It then introduces solutions from Analog Devices for intelligent motion control, including power, sensing, and networking components, and discusses how they are applied.
Electric motors are foundational to industrial motion control, accounting for as much as 70% of the power used in industry. This percentage of industrial power represents about 50% of worldwide electrical power consumption. This is why so much effort has been placed into improving motion control efficiency, with intelligent motor control bringing many benefits.
Servo-motor robotic actuators
This inverter-driven motor enables significant reduction in energy consumption
Early motion control relied on basic power-grid-connected motors, and this has evolved into sophisticated multi-axis servo-motor robotic actuators. This evolutionary development has tracked the increasing complexity needed to deliver the higher levels of efficiency, performance, reliability, and self-sufficiency required in smart manufacturing.
The various types of motor control include:
- Fixed speed: The oldest and most basic motion controls are based on grid-connected 3-phase AC motors operating at a fixed speed. Switchgear provides on/off control and protection circuitry. Any required reduction in output is achieved mechanically.
- Inverter-driven motor: The addition of a rectifier, DC bus, and 3-phase inverter stage creates a variable frequency and variable voltage source that is applied to the motor to enable variable speed control. This inverter-driven motor enables significant reduction in energy consumption by running the motor at the optimum speed for the load and application.
- Variable speed drive (VSD): Used for applications needing additional precision for control of motor velocity, position, and torque, VSD achieves this control by adding current and position measurement sensors into the basic voltage-regulated inverter drive.
- Servo-driven system: Multiple VSDs can be synchronized into multi-axis servo-driven systems to accomplish even more complex motion for applications such as computer numerical control (CNC) machine tools where extremely accurate position feedback is needed. CNC machining commonly coordinates five axes and may use as many as twelve axes of coordinated motion.
Multi-axis motion control
At each stage in the development of motion control systems, the complexity has increased
Industrial robots combine multi-axis motion control with mechanical integration and advanced control software to enable three-dimensional positioning along six axes, typically. Collaborative robots, or cobots, are intended to operate safely alongside humans. They are built on industrial robotic platforms by adding safety sensing, as well as power and force-limiting capabilities to supply a functionally safe robotic workmate.
Likewise, mobile robots use functionally safe machine control, but they add localization sensing, route control, and collision avoidance to the robotic capabilities. At each stage in the development of motion control systems, the complexity has increased, often significantly. There are four key factors driving intelligent motion systems:
- Reduced energy consumption
- Agile production
- Digital transformation
- Reduced downtime to ensure maximum asset utilization
High-efficiency motors
Digital transformation involves the capacity to network motion control and extensive sensor data
The adoption of high-efficiency motors and lower-loss VSDs, as well as the addition of intelligence to motion control applications, are key factors in achieving significant energy efficiency through smart manufacturing. Agile production hinges on rapidly reconfigurable production lines. This flexibility is needed to respond to fluctuating consumer demand for a diverse range of products in smaller quantities, requiring a more adaptable production setup. Industrial robots play a pivotal role in executing complex and repetitive operations, thereby increasing throughput and productivity.
Digital transformation involves the capacity to network motion control and extensive sensor data from the entire production facility and share this data in real time. Such connectivity enables cloud-based computing and artificial intelligence (AI) algorithms to optimize manufacturing workflows and enhance asset utilization.
Initial installation costs
Asset utilization serves as the foundation for various new business models and focuses on the productivity of factory assets, not just the initial installation costs. System suppliers are increasingly interested in billing for services based on the uptime or productivity of these assets.
Analog Devices offers multiple devices in each area for designers to consider when updating older designs
This approach leverages predictive maintenance services, which rely on real-time monitoring of each machine asset to boost productivity and minimize unplanned downtime. The key areas that designers must prioritize are power electronics, motion control, current sensing, position sensing, network interfacing, and machine health monitoring. Analog Devices offers multiple devices in each area for designers to consider when updating older designs or starting anew.
Monolithic transformer technology
Power electronics facilitate the power conversion from DC to pulse width modulated (PWM) power inputs in a motor drive system. The power conversion in a motor drive system begins with a high-voltage DC source, typically derived from the AC power mains. As illustrated in Figure 2, the power electronics section is configured using a three-phase half-bridge topology with MOSFETs.
The gates of the upper MOSFETs are floating relative to ground and require an isolated driver. A suitable option is Analog Devices’ ADUM4122CRIZ. This is an isolated gate driver that provides up to 5 kilovolts (kV) root mean square (rms) isolation. The high level of isolation is achieved by combining high-speed complementary metal-oxide semiconductor (CMOS) and monolithic transformer technology. This gate driver features adjustable slew rate control, which minimizes switching power loss and electromagnetic interference (EMI). This is particularly important if gallium nitride (GaN) or silicon carbide (SiC) devices are used, given their faster switching speeds.
Half-bridge switching devices
The output stages of both the low-side and high-side drivers are floating and not connected to ground
The lower MOSFETs have their source elements referenced to ground and can use Analog Devices’ LTC7060IMSE#WTRPBF, a 100 volt half-bridge driver with floating grounds.
The output stages of both the low-side and high-side drivers are floating and not connected to ground. This unique double-floating architecture makes the gate driver outputs robust and less sensitive to ground noise. Additionally, the devices incorporate adaptive shoot-through protection with programmable dead time to prevent both half-bridge switching devices from turning on simultaneously.
Motion control system
The motion controller serves as the brain of the motion control system. Acting as the central processor, it generates the PWM signals that drive the power electronics. These signals are based on commands from a central control center and feedback from the motor, such as current, position, and temperature. The controller dictates the motor's speed, direction, and torque based on this data. Often located remotely and implemented through an FPGA or a dedicated processor, the controller requires isolated communication links.
The controller dictates the motor's speed, direction, and torque based on this data
For this purpose, a serial data link like Analog Devices’ ADM3067ETRZ-EP can be used. This is an electrostatic discharge (ESD) protected, full-duplex, 50 megabit per second (Mbps) RS485 transceiver. It is configured to provide high-bandwidth serial communications from the position feedback sensors back to the motion controller. This serial line is protected from ESD up to ±12 kV and can operate over a temperature range of -55 to +125°C.
Primary feedback parameter
Current feedback from the motor is the primary feedback parameter for control. As current feedback determines the overall control bandwidth and dynamic response of the motion control system, the feedback mechanism must be highly accurate and have high bandwidth to ensure precise motion control.
There are two commonly used current measurement techniques:
- Shunt-based measurements require the insertion of a low-value resistor or shunt in series with the conductor being measured. The differential voltage drop across the shunt is then measured, usually with the help of a high-resolution analog-to-digital converter (ADC). Shunt current measurements are limited by the voltage drop and power dissipation in the shunt resistor and are confined to low-to-medium current applications.
- Magnetic current sensing measures the current by evaluating the magnetic field in the vicinity of the conductor using contactless anisotropic magnetoresistance (AMR) measurements. The resistance of the AMR device, which varies with the magnetic field and hence the current, is measured using a resistance bridge.
High current measurements
The measurement is also electrically isolated from the measured conductor
Magnetic current measurement eliminates the voltage drop and subsequent power loss in shunt resistors, making it better suited for high current measurements. The measurement is also electrically isolated from the measured conductor.
For isolated current measurements, the Analog Devices’ ADUM7701-8BRIZ-RL can be used. This is a high-performance, 16-bit second-order sigma-delta ADC that converts an analog input signal, from a current sense voltage drop across a sense resistor, into a high-speed, single-bit digitally isolated data stream.
Current measurement device
An alternate current measurement device is the AD8410AWBRZ high-bandwidth current sense amplifier. This is a differential amplifier with a gain of 20, a bandwidth of 2.2 megahertz (MHz), and low offset drift (~1 microvolts per degree Celsius (μV/°C)). With a DC common mode rejection ratio (CMRR) of 123 decibels (dB), it can handle bidirectional current measurement with common mode inputs of up to 100 volts.
An alternate current measurement device is the AD8410AWBRZ high-bandwidth current sense amplifier
Rotational position sensing based on AMR magnetic position sensors offers a more cost-effective alternative to optical encoders. These sensors have the added benefit of being robust in industrial environments, where they are often exposed to dust and vibrations. Feedback on the motor shaft angle can be used for direct position control in servo systems or for determining rotational speed.
Surrounding magnetic field
The ADA4571BRZ-RL is a magnetoresistive angle sensor that uses dual temperature-compensated AMR sensors to detect shaft angle over a range of 180° (±90°) with an accuracy of <0.1° error (<0.5° over life/temperature). This device produces both sine and cosine single-ended analog outputs that indicate the angular position of the surrounding magnetic field. The device can operate in magnetically harsh environments and does not suffer degradation of angular readout error with wide air gaps.
The outputs of the angle sensor can be connected to the Analog Devices’ AD7380BCPZ-RL7, a dual, 16-bit input, successive approximation register (SAR) ADC. This ADC samples simultaneously on both differential input channels at up to 4 megasamples per sec (MSPS). An internal oversampling function improves performance.
Slower operating conditions
Oversampling is a common technique employed to increase ADC accuracy
Oversampling is a common technique employed to increase ADC accuracy. By capturing and averaging multiple samples of the analog input, this function reduces noise, using either normal average or rolling average oversampling modes. Oversampling can also help achieve higher accuracy under slower operating conditions.
Smart manufacturing relies upon a network of intelligent motion applications that share data between the machines on the factory floor and the central control and management network. This sharing requires robust connectivity. For this, designers can use Analog Devices’ low-power and low-latency Ethernet physical layers (PHYs), including the ADIN1300CCPZ Ethernet PHY transceiver. Operating at data rates of 10, 100, or 1000 megabits per second (Mbits/s), the ADIN1300CCPZ is designed to operate in harsh industrial environments, including ambient temperatures up to 105°C.
Reducing unplanned downtime
Switches are used to route Ethernet connections. Analog Devices offers an industrial Ethernet Layer 2 embedded dual-port switch, the FIDO5200BBCZ. The switch complies with IEEE 802.3 at 10 and 100 Mbits/s, and it supports both half and full-duplex modes to support PROFINET, Ethernet/IP, EtherCAT, Modbus TCP, and Ethernet POWERLINK industrial Ethernet protocols.
Machine health monitoring employs sensors to measure physical parameters such as vibration
Machine health monitoring employs sensors to measure physical parameters such as vibration, shock, and temperature, providing real-time insights into a machine's condition. By logging this data during standard motion control operations and analyzing it over time, it becomes possible to accurately assess the machine's mechanical health. This data-driven approach allows for predictive maintenance schedules, which not only prolong the machine's operational life but also significantly reduce unplanned downtime.
Intelligent motion control
Applying machine health requires, vibration and shock sensors be installed into the motor. The ADXL1001BCPZ-RL ±100 g microelectromechanical systems (MEMS) accelerometer is an example of a low-noise sensor with a -3 dB bandwidth of 11 kilohertz (kHz). It is a high bandwidth and lower-power alternative to piezoelectric sensors. For applications that require measurement along three axes, the ADXL371 can be a suitable choice.
Intelligent motion control is critical to enable smart factories, and it requires carefully chosen electronic components to be implemented effectively. As shown, many of these components are already curated to kickstart a design.
They include power electronics to drive the motor, current and position sensors to provide accurate feedback data for precise and accurate motion control, industrial network connectivity to provide system-level insights to optimize manufacturing flow, and vibration and shock sensors to enable machine health monitoring to reduce unplanned downtime and extend the operational life of assets.
