Several key sensor technologies that play a major role in today's robots include magnetic position sensors, presence sensors, gesture sensors, force and torque sensors, environmental sensors and power management sensors.
Magnetic Position Sensors
Magnetic angular position sensor integrated circuits (ICs) are one of the most widely used sensor technologies in consumer, service professional, social and even industrial robots today. Today, almost every joint in a consumer, service professional or social robot uses two or more magnetic angular position sensor ICs.
For each axis of motion or joint rotation, at least one magnetic angular position sensor is used. Many of today's robots use small but powerful brushless DC motors (BLDC) to move the robot's joints and limbs. In order to properly drive the motors, motor position feedback is required.
In addition, closed-loop motor control of the robot joints also requires joint gear angle position feedback. Therefore, for the robot joints, two magnetic angular position sensors are required on each axis of motion, and the magnetic angular position sensor ICs can provide motor commutation feedback to the joint motor controller.
Robotic arm with magnetic position sensor
For example, a total of four magnetic position sensors are used for a robot ankle that requires axial motion in both pitch and roll. By having this type of multiple connections per joint, and recognizing the large number of joints required for most robots, it is clear why magnetic angular position sensors are so prolific in today's latest robotic products.
Presence Sensors
Today, several presence sensor technologies are integrated into today's robots and their information is fused to provide robotic spatial vision sensing as well as object detection and avoidance. 2D and 3D stereo vision cameras are commonly found in many of today's new consumer and professional service robots.
However, new advanced sensor technologies such as time-of-flight sensors including Light Detection and Ranging (LIDAR) sensors are also increasingly being deployed in robots.LIDAR provides a high-resolution 3D mapping of the space in which the robot is operating and its surroundings so that it can better perform tasks and move around.
LiDAR mapping
Similarly, ultrasonic sensors are used for presence sensing. Like their counterparts in automobiles used for security alarm systems when on standby, ultrasonic sensors in robots are used to detect nearby obstacles and prevent them from crashing into walls, objects, other robots, and among humans.
Moreover, they can play a role in robots that perform major functional tasks. Thus, ultrasonic sensors play an important role in near-field navigation and obstacle avoidance, ultimately providing overall improved robot performance and safety.
However, ultrasonic sensors have a limited range, ranging from about one centimeter to several meters, and a maximum orientation cone of about 30°. They are relatively inexpensive and offer good accuracy at close ranges, but their accuracy decreases with increasing range and measurement angle.
They are also susceptible to temperature and pressure variations and to interference from other proximity robots that use ultrasonic sensors tuned to the same frequency. However, when used in combination with other presence sensors, they can provide useful and reliable position information.
When data from all of these presence sensors (2D/3D cameras, LIDAR, and ultrasound) are fused together, as we are now beginning to see in high-end consumer/professional service robots and industrial robots, these robots are able to achieve spatial awareness and move and perform more complex tasks without damaging themselves, people, or their surroundings.
Gesture Sensors
Gesture sensors are also increasingly being integrated into some of today's most sophisticated robots to help provide user interface commands. Gesture sensor technology includes optical sensors and control arm band sensors worn by the robot operator.
Using optical-based gesture sensors, robots can be trained to recognize specific hand movements and perform certain tasks based on specific gestures or hand movements. These types of gesture sensors offer many opportunities in the home or hospital for people with disabilities and limited communication capabilities as well as in smart factories.
Using armband-controlled sensors, the wearer can communicate and control collaborative, industrial, medical or military robots to perform and/or mimic certain tasks based on how the operator moves and gestures his or her arm. For example, a surgeon wearing armband sensors on each arm can control a pair of telemedicine robot arms to perform surgery, possibly as far away as the other side of the globe.
Force-Torque Sensors
Force-torque sensors are also increasingly used in today's next-generation robots. Force-torque sensors are not only used in end-effectors and grippers of robots, but are now also used in other parts of the robot, such as the torso, arms, legs and head. These specialized force torque sensors are used to monitor limb velocity movements, detect obstacles and provide safety alerts to the robot's central processor.
For example, when a force torque sensor in a robot arm detects a sudden and unexpected force due to the arm striking an object, its control safety software may cause the arm to stop moving and retract to its position.
The force torque sensor is also used in conjunction with presence sensors as well as other safety monitoring sensors, such as environmental sensors, to provide overall safe area monitoring capabilities.
Environmental Sensors
A variety of environmental sensors are also making their way into industrial and consumer robotics. Environmental sensors that can detect VOCs (volatile organic compounds) regarding air quality, temperature and humidity sensors, pressure sensors, and even sensors that can detect lighting. These sensors not only help ensure that robots can continue to operate efficiently and safely, but also make robot locals aware of unsafe environmental conditions.
Power Management Sensors
Power management sensors are also integrated into today's automated robots to help extend the operating time of the robot between charges and to ensure that lithium-ion batteries, the most common batteries used in today's automated robots, are not overcharged or drained while in use. See Figure 4.0.
Power management sensors are also used in the areas of voltage regulation as well as power and thermal management of robot joint motors. All on-board robotic electronics, such as microprocessors, sensors, and actuators, require low-noise ripple power supplies and regulation to ensure that they work efficiently and correctly.
The latest sensor solutions for robotic power management include coulomb counting for battery discharge and charge, accurate and reliable overheat monitoring sensors for voltage regulators, and current sensors in battery management devices.
Thanks to the integration and fusion of all these new sensor technologies, today's latest robots can operate more independently and safely. In addition, thanks to significant improvements in computing power, software and artificial intelligence, and working in concert with these new sensor technologies, these next-generation robots can be adapted more easily to a wide range of application requirements.
Moreover, they can perform tasks more accurately and faster than their predecessors. Finally, they can operate and work more independently, collaboratively and safely with humans in a wider range of home, business and manufacturing environments.