Signal reception
Last year, a refrigerated truck of a logistics company broke down in Heilongjiang at minus 25 degrees. The driver pressed the outrigger button three times but it didn’t respond. Later, it was found that the remote control battery had insufficient voltage at low temperatures. The signal reception of the electric outrigger of the truck is like an experienced driver stepping on the clutch, which requires the coordination of force and timing.
When the driver presses the control button, the signal must pass three levels before it can take effect. First, it must pass the heartbeat detection of the on-board CAN bus. This mechanism is exactly the same as the anti-mistouch design of the truck ECU. If the signal lasts less than 0.3 seconds, it will be filtered out directly. Then it must pass the voltage fluctuation test, especially the circuit interference problem often encountered by modified vehicles. Last year, there was a case where the wiring harness was improperly routed during the modification of the car audio, causing the outrigger signal to be swallowed by the radio electromagnetic wave.
The most terrible thing is signal conflict processing. For example, a common scenario in RVs: on one side, the outriggers are deployed with the remote control, and on the other side, the onboard computer automatic leveling system is also sending instructions. At this time, the arbitration chip in the control box has to direct traffic like a traffic policeman, and the priority level setting is particularly particular. Usually manual operation has the highest authority, but when the tilt sensor alarm is encountered, the safety command will automatically jump the queue.
There is a particularly interesting design detail – many new electric outriggers have two sets of signal decoding solutions hidden in the control box. Just like the “dual clutch backup” often said by truck drivers, one set handles conventional PWM pulse signals, and the other set is specifically for the switch signal of the old relay. Last year, I helped the modification factory solve a difficult problem: the outriggers of a European imported RV were incompatible with the domestic control system. In the end, it was found that the signal pulse width differed by 15 milliseconds, and it was solved by changing the resistance value.
System detection
A thrilling scene happened in a RV camp last year: when tourists deployed the outriggers, the four legs landed at different speeds, and almost threw the roof solar panel off. This detection system is like the eyes of an old repairman. It not only looks at the landing speed of the outriggers, but also listens to the working sound of the hydraulic pump.
Every time the outriggers are started, the system must complete five key checks. First, let the angle sensor confirm the vehicle’s inclination, which can reach an accuracy of 0.5 degrees, which is more accurate than the gyroscope on a mobile phone. Then the pressure sensor starts to work, sensing the hardness of the ground like a Chinese medicine pulse-the feedback pressure of cement and mud can differ by more than three times. The most intelligent is the speed synchronization detection. The speed difference of the four outrigger motors cannot exceed 5%, otherwise an emergency stop will be triggered immediately.
The handling strategy for encountering special terrain is particularly particular. For example, when the outriggers are deployed on a slope, the control system will automatically enter the “mountain climbing mode”. At this time, the outriggers on the uphill side will be extended by 20 mm, just like when people climb a mountain, they must step firmly on the front foot. Last year, the snow mode of a certain brand of RV was tested. After the outriggers touched the ground, they would apply an additional 10 seconds of continuous pressure to prevent the frozen soil from melting and causing unstable support.
Predictive maintenance functions are now becoming more and more intelligent. A modification factory showed me their data: by analyzing the current curve when the outrigger motor starts, it can predict gear wear 200 operations in advance. Just like an experienced driver listening to the engine sound to judge the vehicle condition, the system will record the vibration spectrum of each outrigger deployment, and directly issue a warning when an abnormal waveform is found.
The biggest headache for the repair shop is actually the problem of false alarms. Last year, a cold chain transport truck always reported insufficient outrigger pressure. After three days of investigation, it was found that the temperature sensor was frozen silly-the plastic shell deformed at minus 30 degrees and caused false touches. Now the new system has added an environmental compensation algorithm, just like the low-temperature start strategy of truck diesel vehicles, and the detection threshold will be adjusted according to the real-time temperature.
Motor start
Last winter, a truck driver in Inner Mongolia couldn’t open the electric outrigger on the frozen grassland at minus 35 degrees-later it was found that the motor carbon brush was frosted. The motor start of the truck electric outrigger is like the cold start of a diesel vehicle, which requires both explosive power and overload protection.
There are two types of DC motors used in electric outriggers: brushed motors are cheap and durable but easy to ignite, and brushless motors are three times more expensive but have a long life. A modification factory owner did the math with me: If you use a brushed motor, you have to clean the carbon powder every 300 starts, otherwise it will affect the speed just like carbon deposits in the engine. Last year, after they replaced the cold chain fleet with brushless motors, the failure rate dropped directly from 3 units per month to 1 unit in half a year.
Current control at the moment of starting is the real skill. A better control system will play “soft start”: only 60% voltage is given in the first 0.5 seconds, and full power output is output after the gears are in place. This trick is the same as the half-clutch start of an old driver. It can avoid the mechanical impact of a “clang” sound and prevent the fuse from burning out. There is a counterexample: In order to pursue speed, a domestic outrigger manufacturer directly rotates the motor from a standstill to full rotation, resulting in a broken drive shaft.
The impact of temperature on the motor is more complicated than imagined. At high temperatures, the winding resistance increases, and the control system must automatically compensate for the voltage; at low temperatures, the grease becomes viscous, and some intelligent systems will first let the motor shake three times – just like a truck driver kicking the tire to defrost in winter. Last year, I tested the preheating function of a certain brand: at -20℃, first pass a small current of 2A to heat the motor, and wait until the temperature sensor rises to 5℃ before officially starting. This method can reduce the startup failure rate by 70%.
The most fatal is the stall protection. When the outrigger hits a stone, the current will instantly soar to 3 times the rated value. A good control system is like an experienced old driver, which can cut off the power supply within 0.1 seconds. There is a particularly typical modification case: when adding outriggers to a dump truck, the repairman forgot to adjust the current threshold, and the motor pushed a dent in the frame. The repair cost was enough to buy five new outriggers.
Power transmission
A RV player suffered a loss on the Sichuan-Tibet line: the four outriggers were doing their own things on the slope, and the body almost turned over. The power transmission system is like the differential lock of an off-road vehicle, which needs to provide sufficient power and intelligent distribution.
The core of the transmission mechanism is the planetary gearbox, and the reduction ratio is usually between 30:1 and 50:1. A modification master gave an analogy: “This is like the climbing gear of a truck gearbox, which converts the crazy power of the motor at 3,000 revolutions per minute into the steady power of the outriggers at 2 centimeters per second.” But the gear material is very particular. Although cast steel parts are cheap, they will wear out after running 10,000 times; powder metallurgy can withstand 50,000 times, and the price will be tripled.
Power distribution is the real black technology. For models with four independent legs, each outrigger has a pressure sensor to compete in real time. It’s like four people carrying a sedan chair. If one corner is heavier, the control system will add more power to that side. Test data of a high-end RV last year showed that this system can control the inclination of the vehicle body within 0.3 degrees, which is more accurate than the leveling of a refrigerator.
When encountering soft ground, the power transmission strategy changes immediately. Some systems will play the “ramming mode”: first let the outriggers press down quickly to test, and pause for 0.5 seconds when encountering resistance, and then continue after the ground settlement stabilizes – this trick is learned from the construction principle of pile drivers. When the outriggers are deployed on the beach, the system will automatically perform three tampings, with the pressure increasing by 20% each time.
The loss monitoring of transmission components is becoming more and more intelligent. Some manufacturers have installed vibration sensors in the gearbox, and can predict faults by analyzing the changes in the spectrum. Just like an old mechanic listening to the abnormal sound of the gearbox, the system will compare the noise characteristics of each outrigger deployment. Data from a logistics fleet showed that 17 bearing failures were discovered in advance by this technology, and the direct losses avoided were enough to buy 20 sets of testing equipment.
The route competition between hydraulic transmission and pure electric drive is also very interesting. The hydraulic system is powerful, but the maintenance is as troublesome as serving ancestors; the electric solution is clean and neat, but the explosive power is slightly inferior. There is a comparative data: to support the same 10-ton load, the hydraulic outrigger only takes 3 seconds, and the electric version takes 5 seconds, but the maintenance cost of the electric system is only one-third of the hydraulic system. Now high-end models are starting to play with electric-hydraulic hybrids, just like hybrid trucks, which use electric motors to start and automatically switch to hydraulic assistance when overloaded.
Landing gear extension
Last year, when a semi-trailer of a logistics company was unloading, the four outriggers suddenly extended out of sync, almost throwing a million-dollar precision instrument out of the car – it was later discovered that gravel had entered the worm gear box. The extension of the electric outrigger is like dancing a mechanical dance, and the coordination of each joint must be perfect.
When starting the extension program, the control system must first pass five levels and cut six generals. First, let the gyroscope confirm the tilt angle of the vehicle body, which can reach an accuracy of 0.3 degrees, ten times more accurate than the mobile phone compass. Then the pressure sensor starts working, sensing the hardness of the ground like a Chinese medicine pulse – the feedback pressure of cement and mud can differ by four times. The most intelligent is the speed synchronization detection, the speed difference of the four outrigger motors cannot exceed 5%, otherwise it will immediately trigger an emergency stop.
The strategy for dealing with obstacles is the real skill. Last year, I saw a thrilling scene in the Gobi Desert in Qinghai: when the outrigger pressed down, it hit the rock, and the intelligent system instantly switched to the “vibration breakthrough” mode – letting the motor impact repeatedly at a frequency of 5Hz, and cooperating with the pressure sensor to adjust the strength in real time.
The adjustment of the extension speed is more complicated than expected. When unloaded, it can reach the fastest speed of 12cm/s, but it has to be reduced to 4cm/s when the load exceeds 8 tons. A modification factory suffered a loss: when installing outriggers on refrigerated trucks, the speed curve was not adjusted. As a result, the inertia was too large during emergency stops and the hydraulic cylinder seal was squeezed out. Now high-end control systems can play “speed ramps”, just like an experienced driver stepping on the brakes first heavily and then lightly, so that the extension speed changes according to the S-shaped curve.
The most fatal is the soft ground response plan. When a certain RV player was camping in the wetland, the outrigger sank 15 cm as soon as it touched the ground. The new generation of systems has added a “ramming mode”: first press down quickly to test, and pause for 0.5 seconds when encountering soft ground, and then continue when the soil density meets the standard. This method is similar to the construction principle of a pile driver, which can improve the support stability by 37%.
Status Feedback
A cold chain fleet suffered heavy losses last winter – the temperature sensor misjudged frost as a leg failure, causing loading and unloading delays and freezing a truck of seafood. The status feedback system is like an old mechanic who is on duty 24 hours a day for the car. It must be sharp-eyed and able to eliminate false alarms.
When the leg is running, 32 sensors are reporting in sync: the pressure sensor mutters “the left side is heavy”, the temperature sensor yells “the motor is hot”, and the angle sensor complains “the body is crooked”. The control system must be like an experienced team leader, picking out the real problem from these mixed messages. Last year, there was a classic case: the vibration sensor alarmed that the gear was worn, but when it was disassembled, it turned out that the fixing bolt was loose – the misjudgment rate is comparable to that of a new mobile phone repairman.
Multi-sensor data fusion is the core technology. A better system will use the Kalman filter algorithm to crush and re-combine the data of different sensors. Just like the traditional Chinese medicine doctor’s comprehensive diagnosis of observation, smell, questioning and palpation, the system will compare three sets of data: pressure curve, current fluctuation and vibration spectrum. Data from a modification factory shows that this algorithm can reduce the false alarm rate from 18% to 3%.
The processing strategy when encountering signal conflicts is particularly interesting. For example, the angle sensor says that the body is tilted 2 degrees, but the pressure sensor shows that the four legs are balanced – at this time the system will start the “voting mechanism”. Last year, the decision logic of a German RV was tested: when more than three sensor data are contradictory, it automatically switches to manual mode and flashes the warning light. This process is exactly the same as the emergency stop processing of CNC machine tools.
Predictive maintenance is getting more and more popular now. By analyzing the current curve when the motor starts, the carbon brush wear can be predicted 300 times in advance. Just like an old driver listening to the abnormal sound of the engine, the system will record the vibration characteristic spectrum of each extension. The actual combat data of a logistics company: 23 bearing failures were discovered in advance with this technology, and the losses avoided were enough to buy 50 sets of testing equipment.