In applications such as computer-assisted surgery, automobile safety, and auto-park systems, robotics is becoming commonplace. Industrial automation, the early automation leader, has driven major advances in robotics and factory automation that have aided both factory safety and production efficiency. Advances have been fuelled by investment in four major technology sectors: sensors, transducers, motors, and control electronics.
Smart Sensors And Simple Sensors
Robotic systems view their environment through sensors. The simple act of picking up an object depends upon many sensors (see the figure). The arm containing the “picking element” must find the object. Typically, image sensors locate objects. However, the object may exhibit other material behaviors such as magnetism or heat that can be detected with other sensor types. Motion control for the arm generally involves accelerometers, along with continuous position feedback from another sensor.
Using simple sensors with all processing in a centralised MCU provides a straightforward structure. But there is the risk that the processor cannot calculate quickly enough or service interrupts quickly enough. The advantages of centralised processing include centralised power requirements and algorithm development. This type of system may enhance flexibility but may also limit maximum performance.
The use of smart sensors moves the decision-making process to the point of interest, in this case the arm and the “the picker,” providing opportunities for improved capabilities, in addition to multiple events that are easily controlled. The disadvantage of limited capabilities places a limit on achievable robotic performance, though. Using distributed control, the system design becomes more complex, but the removal of a central bottleneck means the design’s capabilities may be significantly enhanced.
Technology companies continue to develop and deploy devices, which assist in moving the field of robotics to the next level. In some cases the sensor and much of the electronics can be integrated into a monolithic solution.
Proximity sensors are perhaps the most important of all sensor types. They can be found in consumer and communications products such as automated teller machines, vending machines, security systems, and leading-edge personal computers. Proximity sensors also are used in the most advanced mobile handsets to disable screens when a user is on a call, preventing accidental hang-up or muting. They are used in safety systems, intrusion detection, and positioning as well.
Intersil’s ISL29028A ambient and infrared light-to-digital converter is a proximity sensor with a built-in IR LED driver and I2C interface. It uses two independent analog-to-digital converters (ADCs) for concurrent measurement of ambient light and proximity. Also, it has a flexible interrupt scheme designed for minimal microcontroller loading.
Smart Sensor Support
To function appropriately, smart sensors require strong support chips, including very low-power and low-noise signal conditioning elements. High-input-impedance instrumentation amps such as the Intersil ISL28274 provide the rail-to-rail inputs and outputs required for sensor applications, with extremely low input bias current and high common-mode rejection ratio (CMRR) for strain and pressure sensing used in tactile robotic applications.
Sensor amplifiers also are support ICs and important contributors to advanced product design. Intersil’s ISL28133 micropower chopper stabilised op amp is optimised for single-supply operation from 1.65 to 5.5 V, with only 18-μA quiescent current and 8-μV maximum input offset voltage, offset temperature coefficient (TC) of just 0.075 μV/°C maximum, and rail-to-rail inputs and outputs. Ideal noise specifications for this type of IC are 1.1-μV p-p typical noise (0.01 to 10 Hz).
Robotics in various forms has stimulated the imagination of many science fiction writers and investment bankers over the last 40 years, as well as created amazing gains in efficiency and productivity. This trend is in full force, through both fast-growing and slow-growing economic conditions. The right combination of smart or simple sensors with the optimal support devices such as instrumentation amplifiers and sensor amps ensures continuing innovation.