Introduction In recent years, robots have gained increasing attention in national security, industrial inspection, and counter-terrorism missions. Many successful robot platforms have been established internationally, such as the Millibot robot from Carnegie Mellon University, the Scout robot from the University of Minnesota, and the Urban robot from iRobot. However, these robots lack the ability to climb walls, walk on ceilings, and navigate pipes. Currently, many experts have researched robots with wall-climbing capabilities. Examples include Ali Sadegh's wall-climbing robot using a vortex rotation device, Kevin Rogers' continuous motion cleaning wall-climbing robot using adsorption technology, Carlos Grieco's six-legged wall-climbing robot using magnetic adsorption technology, Shigeo HIROSE's wall-climbing robot using magnetic adsorption technology, Professor Pan Yingjun of Chongqing University's walking wall-climbing robot using magnetic adsorption technology, and a wall-climbing robot designed by American scholars using a propeller as a power source. However, these robots suffer from drawbacks such as large size, high cost, heavy weight, poor turning characteristics, and complex control systems, which greatly limit their application. This article introduces a magnetically driven micro-wall-climbing robot, which adopts electromagnetic adsorption technology and the inchworm motion principle. It has the characteristics of simple structure, light weight, easy processing and manufacturing, flexible control, simple control circuit, and fast turning speed. 2 Structure and motion principle of the wall-climbing robot 2.1 Structure of the wall-climbing robot The diagram shows the external structure of the micro-wall-climbing robot. This micro-robot adopts electromagnetic drive technology and is composed of front and rear baffles (1, 3), soft magnet (2), drive coil (4), front and rear feet (5, 8), permanent magnet (6), guide rail (7), micro motor (9), small support (10), torsion spring (111), large support (12), and rotating shaft (13). The robot consists of a large support frame fixedly connected to a micro motor, a small support frame fixedly connected to a torsion spring, and a sliding connection between the torsion spring and the large support frame via guide holes on the support frame. The large and small support frames are connected by a rotating shaft. The shaft of the micro motor is fixed to the small support frame, which is then fixed to the front baffle. The front feet are fixed to the micro motor, the rear feet and permanent magnet are fixed to the rear baffle, and the soft magnet is fixed to the front baffle. The front and rear baffles are connected by two pairs of sliding guide rails. The robot's movements are achieved by utilizing the relative motion between the energized soft magnet and the permanent magnet. This is achieved through the interaction of a linear motion magnetic actuator composed of a push-pull magnetic circuit and a robot foot coil wound with a portal permalloy soft magnet. Utilizing the principle of "like poles repulsion and unlike poles attraction" between the soft and permanent magnets, a series of timing pulse control signals are applied to the coil to change the polarity or movement of the soft magnet, thus mimicking the movement of an inchworm and enabling the robot to climb walls. 2.2 The motion principle of the wall-climbing robot is illustrated in the diagram of its linear movement. Assume the initial state (state 1) is when the coils are not energized. In this state, control timing signals are sent to the robot's front foot (coil 1), rear foot (coil 2), and the driver (coil 3). During the time interval t1 to t2, coil 1 is not energized, while coils 2 and 3 are positively charged. The robot's front foot takes a step forward under the interaction of the soft and permanent magnets. During the time interval t2 to t3, coil 1 is positively charged, coil 2 is not energized, and coil 3 is negatively charged. The robot's rear foot follows with a step under the interaction of the soft and permanent magnets, completing one gait. By repeatedly executing states 1 to 4, continuous linear motion of the robot can be achieved. This is a schematic diagram of the robot's turning and movement principle. Assuming the coils are not energized (initial state 1), the control timing signals shown in Figure 5 are applied to the robot's front foot (coil 1), rear foot (coil 2), driver (coil), and micro motor (coil 4). During the time interval t1-t2, coils 1 and 3 are not energized, while coils 2 and 4 are positively charged. The robot's front foot rotates an angle under the action of the micro motor, as shown in state 2 of Figure 4. During the time interval t2-t3, coil 1 is positively charged, while coils 2, 3, and 4 are not energized. Under the action of the torsion spring, the robot body rotates the same angle as the front foot, completing the robot's turning process and reaching the predetermined position. After time t3, the robot begins to move in a straight line. Since mechanical systems all have a response lag, a time difference can be designed between coils 1 and 2 and coils 3 and 4 in actual operation to make the robot's movement more stable. 3. Generation of Drive Signals As can be seen from the robot's motion principle, various motion states of the robot can be achieved by continuously supplying the control signals shown in Figures 3 and 5 to the coils. This is a system block diagram for generating these drive control signals. Using C or assembly language in an AT89C52 microcontroller, six pulse control signals (two for the micromotor and two for the driver) are programmed to generate the entire wall-climbing robot. Four of these signals are connected to two LG9110 forward/reverse drive chips to control the micromotor and driver, while the other two are connected to two SN75451/SN75452 chips to control the robot's front and rear feet. 4. Experimental Testing Due to the complex magnetic field distribution, it is impossible to perform theoretical analysis and calculation of the driving force of the entire actuator. Therefore, the force gauge device shown in Figure 7 was designed. The actual test results showed that the vertical force of the wall-climbing robot actuator was F1, and the driving force was F2. The device mainly consists of clamps 3 and 5, a three-dimensional micro-displacement stage 1, and two high-precision micro-force measuring instruments 6 and 7. During measurement, the soft magnet 4 and the permanent magnet 2 were mounted on the force gauge device, and the measurement was performed by adjusting the three-dimensional micro-displacement stage. As shown in Figure 8, the vertical distance between the permanent magnet and the soft magnet is σ mm, and the horizontal displacement is x mm. The test curves of the relationship between static vertical force F1 and σ of the walking robot and the crawling robot are obtained by using the force measuring device in reference [5] and the force measuring device shown in Figure 7. The test curves of the relationship between dynamic vertical force F1 and σ are obtained by using the force measuring device in reference [5]. Figure 11 is the test curve of the relationship between dynamic driving force F2 and x. Curve 1 represents the wall-climbing robot and curve 2 represents the walking wall-climbing robot. It can be seen that the dynamic and static vertical force F1 of the wall-climbing robot is close to 0, and its driving force F2 is more than 3 times that of the walking wall-climbing robot. The test curves of the relationship between the walking speed and the driving signal frequency of the wall-climbing robot are obtained by using the force measuring device in reference [5] and the force measuring device shown in Figure 7. Curve 1 represents the speed of the wall-climbing robot, curve 2 represents the speed of the walking wall-climbing robot, and curve 3 represents the theoretical speed of the wall-climbing robot. The two robots used in the experiment are the walking wall-climbing robot and the crawling wall-climbing robot . All the above test results were completed under the following conditions: (1) 700 turns of coil; (2) 5 V control signal voltage; (3) σ=1 mm. Conclusion Experiments show that: (1) Compared with the control signal frequency used in references [5-8] to achieve the purpose of turning the robot, the turning action of this wall-climbing robot is more accurate and faster, and the control is simpler. If the micro motor is replaced with a micro stepper motor, the turning angle can be precisely controlled; (2) The number of turns of the robot drive coil is about 700 turns, and it is best to form a closed magnetic circuit; (3) The closer the distance between the permanent magnet and the electromagnet, the better; (4) By optimizing the design of the control timing signal, the running stability of the robot can be improved; (5) The robot weighs about 30 grams, has a volume of 30 mm × 15 mm × 20 mm, and can move at a speed of 1.1 cm/s. It can climb on a magnetic surface from 0 to 90°; (6) In order to prevent the robot from "derailing" during the movement, a limiting mechanism needs to be added to the robot.