A robot wireless charging device with safety protection and a control method thereof

Abstract

This invention discloses a wireless charging device for robots with safety protection and its control method, relating to the field of wireless charging technology for robots. The device includes a charging base, which integrates a wireless charging transmitter module, an electromagnet array, a base control unit, and a safety protection unit. The safety protection unit is equipped with a hardware watchdog timer, an emergency stop button, multi-dimensional sensors, and independent three-input hardware logic AND gate circuits to achieve triple interlocking: MCU enable, watchdog normal operation, and emergency stop not triggered. The control method is as follows: after the external robot is positioned, a foreign object detection is performed. If the detection is successful, the electromagnet uses PWM soft-start to attract and fix the robot. After confirming the attraction, wireless charging begins. The charging process monitors the operating status in real time, and all outputs are simultaneously cut off when the robot is fully charged, receives a remote release command, or an abnormality occurs. This invention solves the problem of easy displacement and tipping during wireless charging through controllable magnetic attraction, has dual hardware and software safety redundancy, supports remote emergency interruption within 50ms, and is suitable for various mobile robots, especially sign language service robots with a high center of gravity.

Description

Technical Field

[0001] This invention relates to the field of wireless charging technology for robots, and in particular to a wireless charging device for robots with safety protection and its control method, applicable to wheeled robots, legged robots, wheeled-legged hybrid robots, AGVs, and sign language service robots with dual-arm structures. Background Technology

[0002] With the rapid development of robotics technology, various mobile robots have been widely used in warehousing and logistics, industrial manufacturing, public services, and other fields. To ensure the continuous operation capability of robots, efficient, safe, and reliable charging devices have become key supporting equipment.

[0003] Traditional robot charging devices are mainly divided into two categories: contact charging and wireless charging. Contact charging technology is mature, low-cost, and highly efficient (typically greater than 90%), but it has inherent drawbacks such as contact wear, oxidation, and poor environmental adaptability. In harsh environments such as dust, humidity, and oil, metal electrodes are prone to poor contact or even short circuits, requiring regular maintenance. In addition, contact charging requires extremely high docking precision; even a slight deviation can lead to charging failure.

[0004] Existing wireless charging devices typically achieve contactless power transmission through electromagnetic induction or magnetic resonance, offering advantages such as low maintenance costs and no spark hazards. However, current technology still has the following shortcomings: First, it lacks a reliable robot positioning and fixation mechanism during charging. Wireless charging requires high alignment accuracy between the transmitting and receiving coils, with allowable offsets typically not exceeding 10% of the coil diameter. When the robot shifts due to uneven ground, external impacts, or its own vibrations, charging efficiency drops sharply or even stops. For humanoid robots with a high center of gravity (such as sign language service robots), shifting can also cause tipping accidents, posing risks of equipment damage and personnel injury. Second, it cannot achieve remote emergency interruption. Existing devices typically automatically cut off power after the battery is fully charged. If the robot receives an emergency task command during charging, it must wait for charging to complete or require manual intervention before leaving, affecting the robot's response speed and service continuity. Third, the safety protection mechanism is inadequate. Most devices only have basic overcurrent and overvoltage protection, lacking hardware-level safety redundancy for abnormal conditions such as electromagnet overheating, communication interruptions, and robot tilting. When the software system malfunctions or the main control chip crashes, the electromagnet may continue to be powered on and heat up, or the wireless charging may continue to operate under abnormal conditions, posing a safety hazard.

[0005] In particular, for sign language service robots (typically bipedal or upper-body humanoid structures that translate sign language in real time through arm movements), their arms move frequently during operation, resulting in large fluctuations in energy consumption. Furthermore, they often need to provide continuous service for several hours in public places (such as hospitals, government service halls, and banks). Once the battery is depleted, not only must the service be interrupted, but due to the robot's complex structure and high center of gravity, it is also more prone to tipping over due to external impacts during charging. Traditional wireless charging lacks active fixing and remote interruption capabilities, making it difficult to meet the high safety and continuous operation requirements of sign language robots.

[0006] Existing literature discloses a mobile robot charging device that actively seeks out and charges the robot via a mobile base, solving the problem of the robot needing to travel back and forth to a fixed charging station. However, it still uses a contact charging interface, which has the problems of high docking accuracy requirements and easy interface damage. Existing literature discloses a bidirectional charging method for robots, which realizes energy sharing between the chassis and the robot body and improves energy utilization, but does not address active fixation and hardware-level safety protection mechanisms during the charging process.

[0007] Therefore, there is an urgent need to develop a new type of wireless charging device for robots that can solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a wireless charging device for robots with safety protection and its control method. This invention aims to solve the technical problems of unreliable positioning, inability to remotely interrupt emergency charging, and imperfect safety protection mechanisms in existing wireless charging devices. It is particularly suitable for service robots with a high center of gravity, such as sign language robots, that require emergency response.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a wireless charging device for robots with safety protection, comprising a charging base; the charging base includes a base shell, a wireless charging transmitter module for wirelessly transmitting electrical energy to an external robot to be charged, an electromagnet array for generating magnetic attraction to attract a ferromagnetic chuck located on the bottom of the external robot to be charged when powered on, a first wireless communication module, a base control unit electrically connected to the wireless charging transmitter module, the electromagnet array, and the first wireless communication module, and a safety protection unit. The safety protection unit includes a hardware watchdog timer, an emergency stop button, a temperature sensor, a current sensor, a foreign object detection module, and a tilt sensor, and also includes independent hardware logic and gate circuits; the drive enable signal of the electromagnet array and the working enable signal of the wireless charging transmitter module are both controlled by three conditions that are simultaneously satisfied: the MCU of the base control unit outputs an enable signal, the hardware watchdog timer is in normal working state, and the emergency stop button is not triggered; when any condition is not satisfied, the independent hardware logic and gate circuits directly cut off the corresponding output circuit, and are not controlled by the software program. The base control unit is configured to: after detecting that the external robot to be charged has arrived and that the foreign object detection has passed, control the electromagnet array to be energized to attract the external robot to be charged; upon receiving a full charge signal from the external robot to be charged or receiving an external release command through the first wireless communication module, control the electromagnet array to be de-energized to release the external robot to be charged, and simultaneously stop the wireless charging output; during the charging process, if abnormal temperature, excessive current, tilt exceeding the threshold, communication failure, or hardware watchdog timeout is detected, immediately cut off the electromagnet power supply and wireless charging output.

[0010] Furthermore, the electromagnet array adopts a pulse width modulation (PWM) soft-start method with a start-up time of 100ms to 300ms to avoid instantaneous high current surges.

[0011] Furthermore, the total magnetic attraction force F of the electromagnet array satisfies: F = k·m·g; where m is the mass of the adapted external device to be charged, g is the gravitational acceleration, and k is the safety factor, with a value ranging from 0.3 to 0.5.

[0012] Furthermore, the wireless charging transmitter module adopts the Qi 1.3 protocol or a customized magnetic resonance protocol, with a rated charging power of 30W to 100W and a module power transmission efficiency of ≥85%.

[0013] Furthermore, the first wireless communication module adopts the BLE 5.2 protocol, with a communication latency of <50ms, and the command uses a rolling code + CRC check mechanism to prevent false triggering and malicious attacks.

[0014] Furthermore, the foreign object detection module adopts the power loss method: the wireless charging transmitter sends a short pulse with a power of 1W for 50ms, and measures the difference between the active power of the transmitter and the feedback power of the receiver. If the difference exceeds the preset threshold of 0.5W, it is determined that there is a metallic foreign object.

[0015] Furthermore, the tilt sensor is a six-axis inertial measurement unit, fixed to the geometric center of the base control unit PCB board, which detects changes in the pitch and roll angles of the base. When the change in any axis angle relative to the initial calibration value is ≥3°, a protection action is triggered.

[0016] A control method for the above-mentioned wireless charging device for robots includes the following steps: S1: The robot waiting to be charged navigates autonomously to the charging base area. The base detects whether the robot has stopped in place using an infrared or Hall effect positioning sensor. S2: If the robot is in position, the base will start foreign object detection. If a metal foreign object is detected, an audible and visual alarm will be triggered and the charging process will be terminated. S3: If the foreign object detection passes, the base controls the electromagnet array pulse width modulation soft start to attract the ferromagnetic chuck at the bottom of the robot. S4: The robot detects the adsorption status through its own adsorption confirmation sensor. If the adsorption is in place, it sends an adsorption confirmation signal to the base via wireless communication. S5: After the base receives the attraction confirmation signal, wireless charging is started. During the charging process, the temperature, current, communication heartbeat and base tilt status are monitored in real time. S6: When the battery is detected to be fully charged, an external release command is received, or any abnormal operating condition occurs, the wireless charging output and the electromagnet power supply will be cut off immediately and simultaneously. S7: After receiving the release confirmation signal, the robot autonomously drives away from the charging base, and the base resets to standby mode.

[0017] The present invention has the following advantages over the prior art: 1. Controllable magnetic positioning and stability: The electromagnet array actively attracts the ferromagnetic chuck on the bottom of the robot, effectively preventing displacement and tipping caused by external collisions or vibrations during charging, ensuring charging efficiency and equipment safety; the electromagnets adopt PWM soft start to avoid inrush current and extend service life. 2. Rapid remote emergency response: Supports sending remote release commands via mobile APP, central dispatch system or remote control. The base can simultaneously cut off the electromagnet and wireless charging output within 50ms, enabling the robot to respond to emergency tasks immediately and achieve "on call". 3. Dual hardware and software safety redundancy: Integrated multi-dimensional monitoring of temperature, current, tilt, foreign objects, and communication, coupled with hardware watchdog and independent three-input AND gate interlock circuit, can forcibly cut off the output even if the MCU crashes or the software malfunctions, preventing safety accidents, and the functional safety level reaches SIL 1. 4. High versatility and low modification cost: It is suitable for various mobile robots with ferromagnetic chucks. No large-scale modification of the robot is required. Only the ferromagnetic chuck and adsorption confirmation sensor need to be added to the bottom to complete the adaptation. 5. Low maintenance cost: It has no mechanical contact wear parts, has complete fault self-diagnosis and protection functions, and is suitable for long-term unattended automated charging scenarios. Attached Figure Description

[0018] Figure 1 Overall structural diagram of the invention; Figure 2 Schematic diagram of the exploded structure of the charging dock; Figure 3 Hardware system block diagram of the charging dock; Figure 4 Flowchart of the base main control state machine; Figure 5 Timing diagram for wireless communication between the base and the robot; Figure 6 Logic diagram of safety interlock between electromagnet and wireless charging hardware. Specific Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. All embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention. Example 1: Overall Structure Implementation

[0020] The device of this invention is a charging base. The shell is injection molded from ABS engineering plastic, with an overall square shape and rounded corners. A thinned charging window is set in the center of the upper surface, with a window wall thickness of 0.8mm-1.2mm. The interior of the base, from top to bottom, consists of: a wireless charging transmitting coil (racetrack-shaped, 3-5mm thick), a ferrite magnetic shielding sheet (1-2mm thick, extending 3-5mm beyond the coil outline on each side), and a transmitting drive PCB board. The electromagnet array consists of two sets of symmetrical electromagnets, fixed on a dedicated mounting plate, with the top surface of the electromagnets flush with the top surface of the transmitting coil.

[0021] The base control unit uses the ESP32-S3 main control chip, which is responsible for sensor acquisition, electromagnet PWM control, wireless charging scheduling, communication interaction, and state machine logic. The safety protection unit integrates an NTC temperature sensor (attached to the surface of the electromagnet coil), an ACS712 current sensor (connected in series with the electromagnet power supply circuit), an MPU6050 tilt sensor (fixed to the geometric center of the PCB board), a TPL5010 hardware watchdog, a physical emergency stop button (normally closed type, connected in series with the 24V main input terminal), and a foreign object detection circuit (based on the power loss method).

[0022] The base has anti-slip pads on the bottom, and a cooling fan, status indicator lights (RGB tri-color LEDs), and a buzzer on the side wall. The first wireless communication module uses a BLE 5.2 module and is equipped with a ceramic antenna. Example 2: Implementation of Equipment Control State Machine

[0023] As shown in Figure 4, the base main controller has seven working states, and the state transition logic is as follows: 1. IDLE (Idle) State: The system enters this state after power-on or reset. All outputs are turned off, and the blue indicator light flashes slowly. The base periodically broadcasts its own status information, waiting for the robot to arrive. If the arrival sensor detects the robot and there is no global fault, it enters the DETECT state.

[0024] 2. DETECT (Foreign Object Detection) Status: Controls the wireless charging transmitter module to send a short pulse of 1W for 50ms, while simultaneously reading the received power from the robot's BMS via BLE. If the power difference ΔP ≤ 0.5W, the foreign object detection is considered successful, and the system enters the MAG_ON state; otherwise, it enters the FAULT state, with fault code E04 and a rapidly flashing red indicator light.

[0025] 3. MAG_ON (Electromagnet engaged) state: Outputs a PWM signal to drive the electromagnet, with the duty cycle increasing linearly from 50% to 100%, and a rise time of 200ms. Simultaneously, the electromagnet current (normal range 0.5A~1.5A) and temperature are monitored in real time. If an engagement confirmation signal (Attached=1) is received from the robot within 3 seconds and the parameters are normal, it enters the CHARGING state; otherwise, it enters the FAULT state.

[0026] 4. CHARGING Status: The wireless charging transmitter is activated, and the green indicator light breathes. It interacts with the robot every 100ms to receive battery voltage, current, and temperature data; and reads tilt sensor data every 50ms. If a fully charged signal or remote release command is received, it enters the DONE or RELEASE status respectively; if an abnormal condition is detected, it enters the FAULT status.

[0027] 5. DONE (Charging Complete) Status: Wireless charging stops, the electromagnet disconnects after a 200ms delay, and the green indicator light remains on. A release completion signal is sent to the robot, and the device returns to the IDLE state after a 5-second delay.

[0028] 6. RELEASE (Remote Release) State: Immediately stops wireless charging and electromagnet output, the yellow indicator light flashes 3 times quickly, and the buzzer sounds twice. Sends a release completion signal to the robot, and returns to IDLE state after a 1-second delay.

[0029] 7. FAULT Status: All outputs are cut off, the red indicator light flashes rapidly, and the buzzer sounds continuously. A fault code is recorded. The system will only return to IDLE status after the reset button is pressed manually or a reset command is sent via the app. Example 3: Hardware Security Protection Implementation Method

[0030] As shown in Figure 6, this invention uses an independent three-input hardware logic AND gate circuit (e.g., using a 74HC08 chip). The three input signals are: signal A (enable signal output by MCU GPIO, active high), signal B (WDO output of hardware watchdog TPL5010, high level during normal operation, low level when watchdog fails), and signal C (signal output from the normally closed contact of the emergency stop button via a pull-up resistor, high level when not pressed, low level when pressed).

[0031] Three signals are input to an AND gate, whose output simultaneously controls the gate of the electromagnet driving the MOSFET and the power enable pin of the wireless charging transmitter module. The AND gate outputs a high level, allowing the electromagnet and wireless charging to operate, only when all three signals are high simultaneously; if any one signal goes low, the AND gate output immediately goes low, and the hardware cuts off all outputs. This circuit operates completely independently of the software, ensuring a safe shutdown even if the MCU crashes or the program malfunctions.

[0032] The software-level protection thresholds are set as follows: power-off protection when the electromagnet temperature is ≥70℃; power reduction to 50% when the wireless charging coil temperature is ≥60℃, and charging stops when the temperature is ≥65℃; overcurrent protection when the electromagnet current is >1.2A; emergency stop when the base tilt angle is ≥3°; and fault lockout when communication with the robot is interrupted for >2 seconds. Example 4: Example of a dedicated application for sign language robots

[0033] This embodiment is applied to a dual-arm sign language service robot in a government service hall. The robot is 120cm tall and weighs 25kg. It has an 80mm×80mm ferromagnetic chuck embedded in its bottom. The average power consumption is 60W, and the peak power consumption for sign language actions is 120W.

[0034] When the robot's battery level drops below 30%, it autonomously navigates back to its original position. After the base completes foreign object detection, the electromagnet is soft-activated within 200ms, generating a total suction force of 120N with a safety factor of 0.49, ensuring stable adhesion to the robot body and preventing tipping. Once adhesion is confirmed, 60W wireless charging is initiated, with the robot's posture and electrical parameters monitored throughout the process.

[0035] When a hearing-impaired person requests assistance in the lobby, the dispatch system issues an emergency task. Within 50ms, the robot completes the command interaction with its base, and the base simultaneously disconnects the magnetic attraction and charging output. The robot then moves away quickly and without resistance to perform the service task. If the charging process encounters a collision or excessive tilting, the hardware circuit immediately cuts off power and triggers an alarm to avoid the risk of equipment damage.

[0036] Actual testing showed that this device can increase the continuous service time of the sign language robot from 4.2 hours to 6.8 hours, shorten the emergency task response time from 23 seconds to 3.5 seconds, and significantly reduce charging displacement and tipping accidents, greatly improving the stability and timeliness of public sign language services.

Claims

1. A robot wireless charging device with safety protection, characterized in that, The system includes a charging base; the charging base comprises a base housing, a wireless charging transmitter module for wirelessly transmitting electrical energy to an external robot to be charged, an electromagnet array for generating magnetic attraction when powered on to attract a ferromagnetic chuck located on the bottom of the external robot to be charged, a first wireless communication module, a base control unit electrically connected to the wireless charging transmitter module, the electromagnet array, and the first wireless communication module, and a safety protection unit; the safety protection unit includes a hardware watchdog timer, an emergency stop button, a temperature sensor, a current sensor, a foreign object detection module, and a tilt sensor, and also includes independent hardware logic AND gate circuits; the drive enable signal of the electromagnet array and the working enable signal of the wireless charging transmitter module are both controlled by three conditions that are simultaneously satisfied, namely, the base control unit's... If any of the following conditions are not met: the MCU outputs an enable signal, the hardware watchdog is in normal working condition, or the emergency stop button is not triggered, the independent hardware logic and gate circuit directly cuts off the corresponding output circuit. The base control unit is configured to: control the electromagnet array to be energized to attract the external robot to be charged after detecting that the external robot to be charged has arrived and the foreign object detection has passed; control the electromagnet array to be de-energized to release the external robot to be charged and stop the wireless charging output at the same time when receiving a full charge signal from the external robot to be charged or receiving an external release command through the first wireless communication module; and immediately cut off the electromagnet power supply and wireless charging output if abnormal temperature, excessive current, excessive tilt, communication loss or hardware watchdog timeout is detected during the charging process.

2. The robot wireless charging device with safety protection of claim 1, wherein, The electromagnet array adopts a pulse width modulation soft-start method, with a start-up time of 100ms to 300ms.

3. The robot wireless charging device with safety protection of claim 1, wherein, The total magnetic attraction force F of the electromagnet array satisfies: F = k·m·g; where m is the mass of the adapted external robot to be charged, g is the gravitational acceleration, and k is the safety factor, with a value ranging from 0.3 to 0.

5.

4. The robot wireless charging device with safety protection of claim 1, wherein, The wireless charging transmitter module adopts the Qi 1.3 protocol or a customized magnetic resonance protocol, with a rated charging power of 30W to 100W and a module power transmission efficiency of ≥85%.

5. The robot wireless charging device with safety protection of claim 1, wherein, The first wireless communication module adopts the BLE 5.2 protocol, with a communication delay of <50ms, and the command uses a rolling code + CRC check mechanism.

6. The robot wireless charging device with safety protection of claim 1, wherein, The foreign object detection module uses the power loss method: it determines whether there is a metallic foreign object by comparing the difference between the active power at the transmitting end and the feedback power at the receiving end.

7. The wireless charging device for robots with safety protection according to claim 1, characterized in that, The tilt sensor is a six-axis inertial measurement unit, fixed on a PCB board inside the base, which detects changes in the pitch and roll angles of the base. When the change in any axis angle relative to the initial calibration value is ≥3°, a protection action is triggered.

8. The wireless charging device for robots with safety protection according to claim 1, characterized in that, The device is compatible with wheeled robots, legged robots, wheeled-legged hybrid robots, AGVs, or sign language service robots with dual-arm structures.

9. A control method for a robot wireless charging device with safety protection as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: The robot waiting to be charged navigates autonomously to the charging base area. The base detects whether the robot has stopped in place using an infrared or Hall effect positioning sensor. S2: If the robot is in position, the base will start foreign object detection. If a metal foreign object is detected, an audible and visual alarm will be triggered and the charging process will be terminated. S3: If the foreign object detection passes, the base controls the electromagnet array pulse width modulation soft start to attract the ferromagnetic chuck at the bottom of the robot. S4: The robot detects the adsorption status through its own installed adsorption confirmation sensor. If the adsorption is in place, it sends an adsorption confirmation signal to the base via wireless communication. S5: After the base receives the magnetic attraction confirmation signal, wireless charging is started. During the charging process, the temperature, current, communication heartbeat and base tilt status are monitored in real time. S6: When the battery is detected to be fully charged, an external release command is received, or any abnormal operating condition occurs, the wireless charging output and the electromagnet power supply will be immediately and simultaneously cut off. S7: After receiving the release confirmation signal, the robot autonomously drives away from the charging base, and the base resets to standby mode.

Images