Robots are more and more frequent in manufacturing and warehousing services. Factories are increasing their use of cell robots to assist autonomously transfer objects from level A to level B with out human interplay, whereas additionally increasing their use of collaborative robots to allow extra environment friendly work and cut back employee fatigue. Present sensing performs a crucial function in cell robots and collaborative robots to assist understand these advantages.
Cellular robots usually function on lithium-ion batteries between 48 V to 80 V on the primary energy rails and will expertise excessive in-rush currents exceeding 150 A on the primary rail. The secondary rails on cell robots can make the most of anyplace between 3.3 V to 80 V to energy peripherals corresponding to lighting, motors, imaginative and prescient methods, CPU, reminiscence, and different related subsystems. Present ranges on the secondary rails are usually a lot decrease, within the vary of tens of amperes.
Alternatively, collaborative robots usually function between 24 V and 60 V. The present degree throughout the system—particularly the present in electrical motors—is often round 20 A or much less per node. Precision present measurements are far more vital in collaborative robots since excessive accuracy gives tight system management to allow protected and environment friendly operation of the robotic.
Present sensing performs an integral half in robotics methods to be used circumstances corresponding to motor-drive phase-current measurements, battery-management methods, and basic peripheral monitoring.
Motor drives in cell and collaborative robots
In motor-control functions, current-sense ICs now have a front-end that leverages a expertise known as enhanced pulse-width modulation (PWM) rejection. This expertise minimizes the output error brought on by switching common-mode voltage indicators, that are quite common with inline section present measurements. As proven in Determine 1, it improves electrical traits corresponding to offset, acquire error and temperature drift, enabling advantages corresponding to enhanced system efficiency and ultra-precise measurements.
Determine 1 PWM rejection improves electrical traits corresponding to offset, acquire error, and temperature drift. Supply: Texas Devices
Wanting extra carefully at a motor drive, Determine 2 exhibits 5 potential places for current-sensing ICs in three-phase motor methods inside cell or collaborative robots. Beginning on the prime left is a high-side DC hyperlink, which is phase-agnostic and displays present hundreds in general motor system in addition to short-circuit situations. The next current-sensing implementation is on the excessive aspect of every section, monitoring the present going into every section of the motor. Monitoring every section allows the system to higher detect which section could also be working incorrectly. For prime-side measurements, the current-sensing ICs usually see the best system voltage ranges.
Determine 2 Here’s a synopsis of motor current-sensing strategies generally employed in robotics methods. Supply: Texas Devices
Transferring to the middle of Determine 2 is inline present monitoring, which allows a closed-loop suggestions system. The controller half can now management the system primarily based on the in-phase present ranges, which gives tighter management capabilities. The problem with inline motor present sensing is the switching common-mode sign; nevertheless, PWM rejection expertise may help mitigate the error {that a} PWM sign may generate, along with sensing excessive common-mode voltages as much as 110 V, just like the high-side measurement. These options make it simpler to implement these ICs in a system and improve general effectivity by enabling tighter system management.
The final configurations in Determine 2 are the low-side section and low-side DC hyperlink. The low-side measurements are usually carried out at decrease voltage ranges as a result of the ICs are near floor; these ICs can monitor the low-side present. Monitoring on the low aspect provides a holistic studying of present measurements within the system; it additionally affords decrease ranges of safety and management after the load. It’s potential to make use of a number of of those configurations in a motor system.
Level-of-load detection in cell and collaborative robots
Determine 3 exhibits how a cell robotic system may monitor peripherals corresponding to lighting, radar, processing methods, and different related subsystems. Usually, the facility system gives DC energy to the secondary rails and channels. Energy is channeled right into a DC/DC converter after which to a load swap, which connects and disconnects the load from the supply to avoid wasting vitality and improve effectivity when the peripheral isn’t wanted.
Determine 3 Here’s a broad view of point-of-load current-sensing strategies utilized in robotics methods. Supply: Texas Devices
When the swap is enabled, a current-sensing IC displays the present and voltage coming by the swap and transmits voltage, present, energy, and different vital data again to the microcontroller by I2C. This information helps make sure the well being of the system and peak effectivity. You would additionally use a current-sensing IC right here, however it could require extra {hardware} normally, corresponding to an analog-to-digital converter (ADC) or a general-purpose enter/output pin on the microcontroller. Nonetheless, in particular cases, the place you want quick overcurrent detection, a current-sensing IC has a 1-µs comparator.
Rising security traits in robots
The Worldwide Group for Standardization (ISO) 3961-4 specifies the security necessities for driverless cell robots and their methods for warehouse robotics, whereas ISO 15066 specifies the security necessities for collaborative industrial robotic methods and their work atmosphere. The ISO requirements differ since a cell robots’ capacity to maneuver round a warehouse or space with considerably extra levels of freedom may lead to an elevated likelihood of an incident with the robotic.
Given the ISO requirements, Automotive Electronics Council (AEC)-Q100 ICs may help guarantee the best ICs high quality, and that the knowledge these ICs are producing is dependable.
Leveraging present sensing in cell or collaborative robotic platforms can enhance security and effectivity, cut back employee fatigue, and assist monitor system well being. There are challenges in implementing current-sensing ICs corresponding to measurement, however small-outline transistor (SOT)-23 or SC-70 packages may help decrease measurement constraints.
Utilizing current-sensing ICs may help designers add enhanced capabilities by enabling tight management and well being monitoring. Present sensing is ever-expanding, and as expertise continues to develop, the usage of present sensing will change into an increasing number of related, since extra electronics will want monitoring.
Kyle Stone is a product advertising engineer at Texas Devices.
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