Energy-saving control method for energy recovery of pneumatic monorail crane

Abstract

The invention relates to an energy-saving control method for energy recovery of a pneumatic monorail crane, which comprises the following steps of: generating a deceleration demand when receiving a deceleration or stop instruction in an operation process, or detecting that the vehicle speed exceeds a preset upper limit, or detecting that the vehicle speed continuously rises under a downlink working condition and reaches a preset overspeed risk criterion; in response to the deceleration demand, when the pressure of the recovery gas storage channel is lower than a preset upper limit, a recovery gas storage channel communication instruction is output, the pneumatic driving unit is controlled to enter a reverse dragging state, and compressed gas generated by reverse dragging is recovered; the vehicle speed change is monitored, and if the vehicle speed does not decrease according to the preset deceleration or does not decrease to the target speed within the preset time, it is judged that the current braking force is insufficient; when it is judged that the current braking force is insufficient, mechanical braking is involved to complement the braking force, communication of the recycling gas storage channel is kept, and compressed gas generated by reverse dragging continues to be recycled; and when the vehicle speed is reduced to the target speed or the parking condition is met, energy recovery braking is quitted, the recovery gas storage channel is closed, and keeping or parking control is switched to.

Description

Technical Field

[0001] This invention belongs to the field of mining equipment technology, specifically an energy-saving control method for energy recovery of a pneumatic monorail crane. Background Technology

[0002] Combining patent applications CN116677676A and CN113479230A, it can be seen that the existing technologies have made improvements in two aspects: hydraulic energy release control and pneumatic monorail descent smooth control. However, a complete technical system for energy recovery and energy-saving control of pneumatic monorails has not yet been formed, and there are obvious deficiencies in control logic, system structure, and functional coverage. First, CN113479230A mainly adjusts the air pressure of the brake cylinder through a pressure reducing valve to achieve uniform descent. Its essence is a passive control method combining air pressure regulation and mechanical friction braking. It relies on manual operation to switch braking modes and lacks an automatic judgment mechanism based on vehicle speed, speed change trend, and running direction. It cannot actively generate deceleration demand when the vehicle speed increases abnormally or there is a risk of speeding. The response is lagging under complex slopes and heavy load conditions, and it is highly dependent on human intervention. At the same time, this solution does not involve an energy recovery path, and all braking energy is dissipated in the form of frictional heat, which not only increases brake wear but also causes energy waste, resulting in limited energy-saving effect. Secondly, although CN116677676A introduces an accumulator to store and release braking energy and improves operational stability through pressure grading and speed deviation control, its core lies in the control of hydraulic energy release, which is a post-event adjustment strategy. It does not involve the coordinated control of deceleration triggering and energy recovery, nor does it establish a mechanism for actively generating deceleration demand based on multi-source information during operation. In particular, it does not proactively control the risk of continuous speed increase during downhill driving. Therefore, it still has shortcomings in terms of the timeliness of braking triggering.

[0003] Secondly, neither technology establishes a coordinated mechanism between energy recovery braking and mechanical braking. The former relies entirely on mechanical braking, while the latter focuses on energy release regulation. Neither has implemented control logic for automatic compensation and continuous energy recovery when braking force is insufficient, making it difficult to balance safety and recovery efficiency. Furthermore, from a system perspective, CN116677676A has a complex structure involving various hydraulic components and sensors, requiring high maintenance standards. While CN113479230A has a simpler structure, its control is coarse, lacking closed-loop and dynamic adjustment capabilities. Neither technology forms a structurally sound and precisely controlled pneumatic energy recovery system. Simultaneously, existing technologies do not address stable control of the recovery path, lack control strategies based on pressure thresholds, hysteresis criteria, or confirmation mechanisms, and do not consider back pressure utilization beyond the energy storage limit. This makes the system prone to fluctuations and insufficient energy utilization. Regarding energy utilization, while the former achieves energy re-release, it does not form a closed-loop path from recovery to reuse, while the latter completely neglects energy reuse. Neither technology establishes an energy supply mechanism for starting or upward traction, resulting in insufficient depth of recovered energy utilization. In summary, existing technologies either focus on the smoothness of mechanical braking but lack energy saving and intelligent control, or focus on hydraulic energy release but lack integration with the pneumatic braking process. Overall, they have not formed a complete energy-saving control method covering deceleration triggering, energy recovery, braking coordination and energy reuse, making it difficult to achieve comprehensive optimization of safety, stability and energy saving. Summary of the Invention

[0004] The purpose of this invention is to provide an energy-saving control method for energy recovery of pneumatic monorail cranes, thereby solving some of the drawbacks and shortcomings pointed out in the background art.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: an energy-saving control method for energy recovery of pneumatic monorail, comprising: receiving a deceleration or stop command during operation, or detecting that the vehicle speed exceeds a preset upper limit, or detecting that the vehicle speed continues to rise under the downhill condition and reaches a preset overspeed risk criterion, and generating a deceleration demand;

[0006] In response to the deceleration requirement, when the pressure in the recovery storage passage is lower than the preset upper limit, a command to connect the recovery storage passage is output, controlling the pneumatic drive unit to enter a state that can be reverse-driven by the load, so that the compressed gas generated by the reverse-driven process is introduced into the recovery storage passage for recovery; during the energy recovery braking state, the vehicle speed change is monitored, and if the vehicle speed does not decrease according to the preset deceleration rate or does not decrease to the target speed within the preset time, it is determined that the current braking force is insufficient.

[0007] When the current braking force is determined to be insufficient, mechanical braking is engaged to supplement the braking force, and the recovery gas storage passage is kept open during the mechanical braking engagement so that the compressed gas generated by the reverse drag continues to be recovered; when the vehicle speed drops to the target speed or the parking conditions are met, the energy recovery braking is disengaged and the recovery gas storage passage is closed, and the vehicle switches to hold or parking control.

[0008] Furthermore, the connection of the gas recovery storage passage adopts a single setting and pressure holding: after generating the deceleration demand, a connection command is output, and then the connection holding condition is that the recovery pressure in the gas recovery storage passage reaches a preset holding threshold; when the recovery pressure is lower than the holding threshold, the gas recovery storage passage is disconnected and the energy recovery braking state is exited.

[0009] Furthermore, when the pressure of the gas recovery storage passage reaches the preset upper limit and the deceleration requirement still exists, the gas recovery storage passage is closed, and the pneumatic drive unit enters the controlled back pressure damping state to provide braking force; if the braking force provided by the controlled back pressure damping is still insufficient, mechanical braking intervention is triggered until the vehicle speed drops to the target speed or the stopping condition is reached.

[0010] Furthermore, after the energy recovery braking is disengaged and the vehicle is put into hold or parking control, when a starting demand or upward traction demand occurs, the compressed gas in the recovery gas storage passage is used to supply air to the pneumatic drive unit; when the vehicle speed reaches the preset starting threshold or the pressure in the recovery gas storage passage drops to the preset lower limit, the system switches to supply air from the main gas source.

[0011] Furthermore, after outputting a connection command, a preset confirmation time limit is set. If the recovery pressure does not reach the preset holding threshold within the confirmation time limit, it is determined that recovery has not been established, the recovery gas storage passage is disconnected, and the energy recovery braking state is exited.

[0012] Furthermore, the preset holding threshold adopts a hysteresis criterion, including a holding upper threshold and a releasing lower threshold; when the recovery pressure is higher than the holding upper threshold, the recovery gas storage passage is kept connected; when the recovery pressure is lower than the releasing lower threshold and continues for a preset holding time, the recovery gas storage passage is disconnected and the energy recovery braking state is exited.

[0013] Furthermore, supplying compressed gas to the pneumatic drive unit using the recovered gas storage passage includes pressure-limited gas supply: when the pressure of the recovered gas storage passage is higher than the preset gas supply upper limit, the gas supply pressure is first limited to the gas supply upper limit before supplying gas to the pneumatic drive unit.

[0014] Furthermore, if insufficient speed increase and a pressure drop rate exceeding a preset value are detected before the vehicle speed reaches the preset starting threshold, the system will switch to supplying gas from the main gas source in advance.

[0015] Furthermore, the duration of gas supply through the gas recovery and storage channel does not exceed a preset maximum duration; when the maximum duration is reached, even if the vehicle speed does not reach the preset starting threshold, the system switches to supplying gas from the main gas source.

[0016] Furthermore, the insufficient increase in vehicle speed is determined by trend judgment: the vehicle speed is sampled at least twice within a preset judgment window. If the vehicle speed increment is continuously lower than the preset minimum increment and the pressure drop rate of the gas recovery and storage passage exceeds the preset value, the system will switch to supply gas from the main gas source in advance, and will prohibit switching back to the gas recovery and storage passage before the vehicle speed reaches the preset starting threshold.

[0017] The beneficial effects of this invention are as follows: By constructing a multi-source triggered deceleration determination mechanism, this invention combines manual command triggering, overspeed determination, and downward overspeed trend risk determination to achieve proactive identification and early intervention of deceleration needs, thereby improving the safety redundancy of the operation process. During deceleration, energy recovery braking is prioritized, allowing the pneumatic drive unit to enter a state where it can be towed by the load, converting the vehicle's kinetic energy into compressed gas for storage, achieving simultaneous braking and energy recovery. When the recovered braking force is insufficient, mechanical braking is automatically initiated, and the recovery path remains connected during mechanical braking intervention, thereby maximizing recovery efficiency while ensuring braking performance and significantly reducing the consumption of the main air source.

[0018] Furthermore, this invention improves the stability of the recovery path control through control strategies such as single-position and pressure holding, hysteresis criteria, and confirmation time limits, avoiding system fluctuations caused by frequent switching. When the gas storage pressure reaches the upper limit, it automatically switches to a controlled back pressure damping state, forming a graded braking structure and improving system safety. Simultaneously, during subsequent start-up or upward traction phases, recovered gas is preferentially used for gas supply, and adaptive adjustment of the gas supply process is achieved through pressure limiting control, trend judgment, gas supply duration limitation, and anti-repeated switching mechanisms. This ensures stable power response and further improves energy utilization, thereby enhancing the overall energy-saving performance and operational reliability of the pneumatic monorail. Attached Figure Description

[0019] Figure 1 This is a functional relationship diagram of the energy recovery and energy-saving control method for pneumatic monorail cranes of the present invention.

[0020] Figure 2 This is a schematic diagram of the pressure change and threshold criterion of the gas recovery and storage passage in Embodiment 1 of the present invention.

[0021] Figure 3 This is a schematic diagram illustrating the relationship between speed and braking force and the intervention of mechanical braking in Embodiment 1 of the present invention.

[0022] Figure 4 This is a schematic diagram of the recovery pressure hysteresis retention and release criteria in Embodiment 1 of the present invention.

[0023] Figure 5 This is a schematic diagram showing the changes in vehicle speed and recovery pressure during the initial stage in Embodiment 2 of the present invention.

[0024] Figure 6This is a schematic diagram illustrating the determination of the pressure drop rate and velocity increment trend in Embodiment 2 of the present invention.

[0025] Figure 7 This is a comparison chart of the effective output of pressure-limited gas supply and non-pressure-limited gas supply in Embodiment 2 of the present invention. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] Combined with appendix Figure 1 This invention discloses an energy-saving control method for energy recovery in a pneumatic monorail. During normal operation, the pneumatic monorail continuously collects operating commands and status parameters, and the control unit determines in real time whether deceleration control is needed. Status parameters include at least the current vehicle speed, speed change trend, and direction of travel. When a deceleration or stop command is received, the control unit directly generates a deceleration request to initiate the subsequent braking control process. When no deceleration or stop command is received, the control unit continues to compare the current vehicle speed with a preset upper limit. If the current speed exceeds the preset upper limit, it is determined that the vehicle is speeding, and a deceleration request is immediately generated. When the vehicle is in a downward direction, the control unit further continuously monitors speed changes. If the speed continuously increases within the continuous sampling period, and the upward trend reaches a preset overspeed risk criterion, it is determined that the vehicle has a stall risk, and a deceleration request is generated in advance. Through this method, the system can not only respond to manually issued deceleration or stop commands but also proactively trigger deceleration control when there is overspeeding or an abnormal increase in downward speed.

[0028] After generating the deceleration demand, the control unit enters the energy recovery braking control process and first detects the current pressure in the recovery air storage passage. When the pressure in the recovery air storage passage is lower than the preset upper limit, the control unit outputs a command to connect the recovery air storage passage, controlling the corresponding valve group to open, thus connecting the recovery air storage passage to the pneumatic drive unit. Simultaneously, the operating state of the pneumatic drive unit is adjusted, changing it from a drive output state to a load-driven reverse-draft state, thereby driving the pneumatic drive unit to rotate in the opposite direction under the vehicle's inertia and load. During the reverse rotation, the gas is compressed, and the resulting compressed gas is introduced into the storage device through the connected recovery air storage passage to achieve energy recovery and create aerodynamic resistance on the vehicle to achieve a braking effect.

[0029] After entering the energy recovery braking state, the control unit continuously collects vehicle speed signals and performs dynamic monitoring, while evaluating the current deceleration effect based on a preset deceleration or target speed curve. If the vehicle speed reduction rate is detected to be lower than the preset deceleration, or if the vehicle speed fails to decrease to the target speed range within a preset time, it is determined that the braking force provided solely by energy recovery is insufficient.

[0030] When the control unit determines that the current braking force is insufficient, it immediately issues a mechanical braking intervention command, controlling the mechanical braking device to participate in the braking process to supplement the insufficient braking force generated by energy recovery. During the mechanical braking intervention, the control unit keeps the recovery air storage passage open and maintains the pneumatic drive unit in a state where it can be towed by a load, so that the vehicle decelerates under the combined action of mechanical braking and pneumatic reverse towing. At the same time, the compressed gas generated during the reverse towing process is continuously introduced into the recovery air storage passage, thereby ensuring braking capacity while continuing energy recovery and improving the overall energy efficiency of the system.

[0031] During deceleration, the control unit continuously monitors vehicle speed changes and operating status. When the vehicle speed decreases to the preset target speed or meets the stopping criteria, the control unit determines that the deceleration process is complete and issues a control command to exit energy recovery braking. Subsequently, it closes the recovery air storage passage, releases the pneumatic drive unit from its reverse-dragging state, and switches to either hold control or parking control state according to current operating requirements. Hold control is used to maintain stable vehicle operation near the target speed, while parking control is used to bring the vehicle to a stable stop and prevent it from rolling away, thus completing the entire deceleration and energy recovery process.

[0032] After generating the deceleration demand, the control unit employs a single-position and pressure-holding control strategy for the connection control of the recovery gas storage passage. When the energy recovery conditions are confirmed, the control unit outputs a single connection command for the recovery gas storage passage, driving the valve assembly to open and establishing a connection between the pneumatic drive unit and the recovery gas storage passage, thus entering the energy recovery braking state. After completing the single connection, the connection signal is not sent repeatedly; instead, pressure-based holding control is implemented.

[0033] After the connection is established, the control unit continuously monitors the recovery pressure within the recovery storage passage and uses whether this pressure reaches a preset holding threshold as the basis for maintaining the connection. When the recovery pressure reaches or exceeds the holding threshold, it is determined that the recovery process has been stably established, the connection of the recovery storage passage is maintained, and energy recovery braking control continues. In this way, frequent start-stop of the passage can be avoided, improving system stability.

[0034] When the control unit detects that the recovery pressure is lower than the holding threshold, it determines that the current recovery state cannot be effectively maintained. At this time, it outputs a disconnect command to close the recovery gas storage passage and exit the energy recovery braking state. Subsequently, the system switches to other braking or control modes to ensure vehicle operation safety and avoid energy loss caused by ineffective recovery processes.

[0035] During regenerative braking, the control unit continuously monitors pressure changes within the regenerative gas storage passage. When the pressure in the regenerative gas storage passage reaches a preset upper limit and deceleration demand still exists, it is determined that the regenerative gas storage capacity has reached its limit, and compressed gas is no longer introduced into the regenerative gas storage passage. The control unit then outputs a shutdown command, and the control valve group closes the regenerative gas storage passage to prevent the gas storage pressure from rising further.

[0036] After closing the regenerative braking passage, the control unit adjusts the operating state of the pneumatic drive unit to enter a controlled back pressure damping state. Specifically, by adjusting the exhaust passage resistance or controlling the opening of relevant valves, a controlled back pressure is formed inside the pneumatic drive unit, thereby generating a stable pneumatic damping force during vehicle movement to replace part of the energy recovery braking function and achieve continuous deceleration.

[0037] Under controlled back pressure damping, the control unit also monitors vehicle speed changes in real time and assesses whether the current braking force meets the deceleration requirements. If the vehicle speed decreases below the preset deceleration or fails to reach the target speed within the preset time, it is determined that the braking force provided by controlled back pressure damping alone is insufficient. At this time, the control unit triggers mechanical braking intervention, so that mechanical braking and pneumatic damping work together until the vehicle speed drops to the target speed or the stopping conditions are met.

[0038] After issuing a command to connect the recovery gas storage passage, the control unit simultaneously starts a confirmation timer, sets a preset confirmation time limit, and continuously monitors the recovery pressure changes within the recovery gas storage passage during this time limit. If the recovery pressure reaches the preset holding threshold within the confirmation time limit, it is determined that the recovery passage has been successfully established, the recovery gas storage passage is maintained, and energy recovery braking control continues. If the recovery pressure still has not reached the holding threshold by the end of the confirmation time limit, it is determined that the recovery process has not been effectively established. At this time, the control unit outputs a disconnect command, closes the recovery gas storage passage, and exits the energy recovery braking state to avoid the impact of ineffective control on system stability.

[0039] To improve the stability and anti-interference capability of connectivity control, a hysteresis criterion is used to set the preset holding threshold, including an upper holding threshold and a lower release threshold. During the recovery process, the control unit continuously monitors the recovery pressure. When the recovery pressure is higher than the upper holding threshold, the recovery state is considered stable, and the recovery gas storage passage is maintained. When the recovery pressure drops below the lower release threshold and remains below it for a preset holding time, the recovery capacity is deemed insufficient to maintain effective recovery. At this point, the control unit closes the recovery gas storage passage and exits the energy recovery braking state. By introducing hysteresis range and duration determination, frequent switching caused by short-term pressure fluctuations can be avoided.

[0040] After disengaging energy recovery braking and switching to hold control or parking control, the control unit continuously monitors operating commands and vehicle status. When a start-up or upward traction demand is detected, compressed gas from the recovered gas storage passage is prioritized as the gas supply source. The control unit outputs a gas supply switching command, connecting the recovered gas storage passage to the pneumatic drive unit, and controls the gas to enter the pneumatic drive unit at a controlled pressure, thereby driving the vehicle to start or providing upward traction. By prioritizing the use of recovered gas, dependence on the main gas source can be reduced, achieving energy-saving operation.

[0041] During the gas supply process, the control unit simultaneously monitors vehicle speed and pressure changes in the gas recovery storage passage. When the vehicle speed gradually increases and reaches the preset starting threshold, it is determined that the vehicle has entered a stable operating phase. At this point, the system switches to supply gas from the main gas source to ensure the stability of continuous power output. Simultaneously, when the pressure in the gas recovery storage passage drops to a preset lower limit, it is determined that the recovered gas reserve is insufficient to maintain effective gas supply. The control unit also performs a gas supply switch, switching the gas source to the main gas source. By controlling the timing of the gas supply switch based on these dual criteria, the system can fully utilize recovered energy while ensuring operational performance, thereby improving the overall system efficiency.

[0042] When supplying compressed gas from the gas recovery storage passage to the pneumatic drive unit, the control unit performs pressure limiting control on the gas supply process. Specifically, before supplying gas, the current pressure in the gas recovery storage passage is detected. When the pressure exceeds the preset upper limit of the gas supply, the control unit limits the gas supply pressure to the pneumatic drive unit within the upper limit range by adjusting the opening of the pressure reducing valve or control valve, and then supplies gas to the pneumatic drive unit to avoid excessive pressure from impacting the system and to ensure a smooth drive process.

[0043] During start-up or upward traction, the control unit continuously monitors changes in vehicle speed and pressure in the regenerative air storage passage. If the vehicle speed has not yet reached the preset start-up threshold, and the rate of increase in vehicle speed is consistently lower than expected, while the rate of decrease in pressure in the regenerative air storage passage exceeds a preset value, it is determined that the current regenerative gas supply capacity is insufficient to support effective acceleration. At this time, the control unit executes a supply switching command in advance, stopping the supply of gas from the regenerative air storage passage and switching to the main gas source to ensure that the vehicle can build up the required power in a timely manner.

[0044] In addition, the control unit sets a maximum duration limit for the gas supply process in the gas recovery and storage channel. A timer starts at the beginning of gas supply, and when the gas supply duration reaches the preset maximum, the control unit switches the gas supply to the primary source, regardless of whether the current vehicle speed has reached the preset starting threshold. Through comprehensive control of the gas supply pressure, supply effect, and supply duration, the reliability and responsiveness of vehicle operation can be ensured while fully utilizing the recovered gas.

[0045] During start-up or upward traction, the control unit uses a trend-based judgment method to evaluate the vehicle speed increase. Specifically, it samples the vehicle speed multiple times within a preset judgment window, obtaining at least two consecutive sample values, and calculates the speed increment between adjacent samples. The control unit compares the speed increment with a preset minimum increment. If the speed increment is lower than the preset minimum increment for multiple consecutive sampling periods, it determines that the speed increase is insufficient, indicating that the current driving force has not been effectively converted into vehicle acceleration.

[0046] Simultaneously, the control unit monitors pressure changes in the reclaimed gas storage passage and calculates its pressure drop rate. When the pressure drop rate exceeds a preset value, it determines that the reclaimed gas is being rapidly consumed and the supply capacity is insufficient. If both conditions are met, the control unit immediately executes a gas supply switching command, stopping the gas supply from the reclaimed gas storage passage and switching to the main gas source to ensure the vehicle receives stable and sufficient driving force. To avoid system instability caused by frequent gas source switching, after the switch is completed, the control unit prohibits switching back to the reclaimed gas storage passage until the vehicle speed reaches a preset starting threshold.

[0047] Example 1:

[0048] In this embodiment, the pneumatic monorail is used for material transportation in the underground auxiliary transport roadway. The total length of the line is 780m, including a 96m long downhill section with a gradient of 6.5% before the transshipment station. The train's tare weight is 4.2t, and the total mass after suspending the hydraulic support accessories is 10.8t, of which the load mass is 6.6t. The train's operating speed before entering this downhill section is 3.00m / s, and the dispatching system requires it to reduce its speed to below 1.00m / s and stop 15m before the station. The effective volume of the gas recovery storage passage is 0.18m³, the initial recovery pressure is 0.42MPa, the upper threshold for holding is 0.55MPa, the lower threshold for release is 0.50MPa, the upper pressure limit is 0.78MPa, the confirmation time limit is 1.2s, the release holding time is 0.8s, and the preset deceleration is 0.45m / s².

[0049] During this transport, the train first passed through a transition section with a relatively gentle gradient. Approximately 58 meters from the station, the driver issued a deceleration command. Based on this, the controller generated a deceleration demand and, following a single-position setting, output a command to connect the gas recovery storage passage, putting the pneumatic drive unit into a state where it could be dragged by the load. Because the gradient at this point was only 3.2%, the reverse drag compression flow was small, and the recovery pressure failed to build up to the upper threshold within the confirmation time limit. The recovery pressure was calculated using the following formula.

[0050]

[0051] In the formula, For a moment The pressure of recycling For the initial recovery pressure, For recycling efficiency, To recover the effective volume of the gas storage passage, This is the converted equivalent flow rate of compressed gas. In this embodiment, we take... During the first period of deceleration demand, take the average. Substitute , , ,get

[0052]

[0053] The calculated pressure is below 0.55 MPa, therefore the system determines that energy recovery has not been established. It then disconnects the energy recovery storage path and exits the energy recovery braking state, thus meeting the control requirement of exiting if energy recovery is not established within the confirmation time limit. Correspondingly, as... Figure 2 As shown, the recovery pressure during the first deceleration demand phase only reached 0.507 MPa at the end of the 1.2s confirmation time limit, which did not exceed the upper threshold of 0.55 MPa. The curve for this phase in the figure is below the upper threshold of 0.55 MPa, indicating that the first set-connection did not form an effective recovery establishment.

[0054] After continuing its descent, the train entered a 6.5% gradient section. Due to the combined effects of heavy load and the gradient, the speed gradually increased from 2.79 m / s to 3.18 m / s, meeting the pre-set overspeed risk criterion for continuous speed increase under descent conditions. The controller then generated a deceleration request again. At this point, the system executed another set-connection operation, the drive unit was reverse-driven by the load, and compressed gas was introduced into the recovery storage passage. Within 0.8 seconds of the second deceleration request starting, the average (q_c) increased to 0.021 MPa·m³ / s. Substituting this into equation... Calculation, there is

[0055]

[0056] This indicates that the recovery pressure has exceeded the upper threshold of 0.55 MPa, the gas recovery and storage passage remains connected, and the energy recovery braking system is officially established. Figure 2 As further shown, after the second deceleration trigger, the recovery pressure quickly crossed the upper threshold and continued to rise in subsequent stages, indicating that under the combined effect of slope and load, the reverse drag compressed gas volume increased significantly, and the recovery gas storage path transitioned from an attempt to establish to a stable holding state.

[0057] Table 1 shows the speed, pressure, and braking status data at key moments during this implementation.

[0058]

[0059] During energy recovery braking, the controller continuously determines whether the deceleration has reached the preset requirement based on the sampled velocity. The determination formula is as follows:

[0060]

[0061] when

[0062]

[0063] Furthermore, if the deceleration process has continued beyond the confirmation time, it is determined that the current braking force is insufficient. In the formula, For the first The actual deceleration of each sampling interval This is a preset deceleration. In this embodiment, we take... , , , ,but

[0064]

[0065] Its speed is less than the preset value of 0.45 m / s², therefore the system determines that regenerative braking alone cannot meet the deceleration target, and immediately intervenes with mechanical braking to supplement the braking force, while keeping the regenerative gas storage passage open so that the compressed gas generated by the reverse drag continues to enter the regenerative gas storage passage. Figure 3 As shown, the vehicle speed decrease slope in the 5.0s to 6.0s range is significantly lower than the preset deceleration requirement, while the total braking force increases from 7.6kN to 9.6kN at 6.0s, corresponding to the start of mechanical braking. Figure 3 The speed curve can also be linearly estimated. The train drops to 1.00 m / s at about 7.44 s, indicating that the mechanical braking intervention can pull the deceleration process back to the target trajectory.

[0066] As the recovery pressure rises further to 0.78 MPa and reaches the set upper limit, while the deceleration demand still exists, the controller closes the recovery gas storage passage, causing the pneumatic drive unit to enter a controlled back pressure damping state. The back pressure damping braking force is estimated according to Equation 3.

[0067]

[0068] In the formula, For back pressure damping braking force, The damping coefficient is obtained through whole-machine calibration. To control the pressure in the back pressure chamber This is the exhaust-side pressure. In this embodiment, it is taken as... , , ,but

[0069]

[0070] For a 10.8t train to achieve a deceleration of 0.45m / s² on a 6.5% gradient, the total braking force required after deducting rolling resistance is approximately 9.95kN. Therefore, there is still a shortfall of approximately 1.38kN. The mechanical brakes continue to output a corresponding compensating force, bringing the total braking force to approximately 10.0kN. The train speed further decreases from 1.95m / s to 1.43m / s, meeting the safety deceleration requirements. This stage... Figure 3 This is reflected in the further improvement of total braking force, in Figure 2 In the middle stage, the recovery pressure stops rising after reaching its upper limit. Both of these correspond to the control action of switching back pressure damping and being supplemented by mechanical braking after reaching the upper limit of pressure.

[0071] To avoid frequent opening and closing of the recovery path near the critical pressure, this embodiment employs a hysteresis criterion composed of a holding upper threshold and a release lower threshold. After the second recovery is established, the recovery pressure fluctuates briefly between 3.6s and 5.0s, but remains above 0.55MPa, thus maintaining the connection. By 8.0s, due to the significant decrease in vehicle speed and weakened reverse compression effect, the recovery pressure drops to 0.49MPa and remains below it for 0.8s. The condition of exceeding the holding upper threshold is no longer met, and the release condition below the release lower threshold is triggered. The system then disconnects the recovery storage path and exits energy recovery braking, switching to holding and parking control. Figure 4 As shown, the recovery pressure curve remained above the upper threshold during the period from 3.6s to 5.0s, indicating that the connection maintenance state was stable. When the recovery pressure dropped to 0.49MPa at 8.0s, the curve fell into the release criterion region and triggered the exit control after 0.8s. This hysteresis method avoids repeated switching caused by pressure fluctuations and ensures the stability of the recovery process.

[0072] During the stopping phase, the mechanical brakes are responsible for maintaining the train's final standstill. The train smoothly stops at the designated position in front of the station in 8.8 seconds, with the stopping error controlled within 0.6m. Based on the speed curve, trapezoidal integral estimation of the entire deceleration process shows that the cumulative displacement of the train from the first deceleration trigger to complete stopping is approximately 19.29m. Combined with the driver issuing the first deceleration command approximately 58m from the station, and subsequent secondary deceleration triggers, mechanical brake intervention, and back pressure damping control, the engineering requirements for deceleration and stopping within 15m in front of the station can be met. During the entire deceleration process, the first recovery attempt was aborted in time due to failure to establish braking, avoiding invalid connection. After the second recovery braking was successfully established, mechanical brake compensation was introduced when braking force was insufficient, and back pressure damping was switched after the pressure reached the upper limit, forming a closed-loop control link that connects energy recovery braking, back pressure damping, and mechanical brake supplementation.

[0073] Example 2:

[0074] In this embodiment, the pneumatic monorail is used as an auxiliary transport line between the underground fully mechanized mining face and the loading chamber. The line has a 88m long, 5.8% gradient downhill section before the loading chamber, and a 132m long, 5.2% gradient uphill section after loading. The vehicle's unloaded downhill mass is 4.5t, and its total mass after loading is 11.2t, of which 6.7t is material. The train's speed before entering the downhill section is 2.80m / s. Before approaching the loading position, it receives deceleration and stopping commands. The controller generates deceleration requirements according to the logic of claim 1, controlling the pneumatic drive unit to enter a load-resistant reverse-dragging state. The compressed gas generated by the reverse drag is introduced into the recovery gas storage passage. When stopping is complete, the pressure in the recovery gas storage passage rises from 0.44MPa to 0.76MPa, and the vehicle smoothly stops 0.5m before the loading position and enters parking control.

[0075] After loading is completed, the train needs to start along the 5.2% uphill track and haul the materials to the transshipment point. Upon receiving the start-up request, the controller prioritizes supplying compressed gas from the recovered gas storage channel to the pneumatic drive unit. To prevent excessively high recovery pressure from causing start-up traction shock, this embodiment sets the upper limit of the recovered gas supply to 0.62 MPa, the lower limit to 0.40 MPa, the start-up threshold speed to 1.20 m / s, the speed sampling period to 0.4 s, the minimum speed increment threshold to 0.06 m / s, the pressure drop rate threshold to 0.11 MPa / s, and the maximum duration of the recovered gas supply to 3.2 s. Since the recovered pressure after stopping is 0.76 MPa, higher than the upper limit, the controller first performs pressure-limiting gas supply before sending the compressed gas to the pneumatic drive unit. Figure 5 As shown, the vehicle speed curve and recovery pressure curve at the start-up stage synchronously reflect the continuous transition relationship between the recovery and pressure limiting stage, the recovery and supply stage, and the main gas source supply stage. The 0.0s to 1.2s stage is the pressure limiting and supply range. At 1.6s, the main gas source is switched in advance. At 3.2s, the vehicle speed reaches the start-up threshold and enters a stable upward traction state.

[0076] The continuous sampling data during the initial stage are shown in Table 2. The table shows that the train can start smoothly initially after the gas recovery supply begins, but as the upward load gradually appears, the speed increment begins to decrease, while the recovery pressure drops more rapidly.

[0077]

[0078] In this embodiment, the controller first determines whether the recovered gas storage is being consumed too quickly based on the rate of decrease in the recovery pressure. The determination formula is as follows:

[0079]

[0080] In the formula, For the first The rate of pressure drop within each sampling interval For a moment The recovery pressure. Taking the 0.8s to 1.2s range as an example, substituting... and , can be obtained

[0081]

[0082] This value is higher than the threshold of 0.11 MPa / s. Further calculations are performed within the 1.2s to 1.6s range.

[0083]

[0084] The levels are also above the threshold, indicating that the gas recovery and storage pathway consumes gas significantly faster during the initial heavy-load upward movement. For example... Figure 6 As shown in the determination graph with the end time of the interval as the horizontal axis, the pressure drop rate bars corresponding to 1.2s and 1.6s reach 0.150MPa / s and 0.175MPa / s respectively, both above the 0.11MPa / s threshold line, indicating that the gas recovery and storage passage showed obvious rapid gas release characteristics in both of these consecutive sampling intervals.

[0085] The controller then makes further judgments based on the upward trend in speed. The trend judgment formula is as follows:

[0086]

[0087] When the length is The decision window continuously satisfies

[0088]

[0089] and

[0090]

[0091] If the vehicle speed increase is insufficient, the primary gas source should be switched earlier. This embodiment uses... As shown in Table 2, the velocity increment in the interval from 0.8s to 1.2s is...

[0092]

[0093] The velocity increment in the 1.2s to 1.6s interval is

[0094]

[0095] Both were below 0.06 m / s, and their corresponding pressure drop rates exceeded 0.11 MPa / s. Therefore, at 1.6 s, insufficient gas recovery was determined, and the controller switched to the main gas source ahead of schedule. At this switch, the vehicle speed was only 0.33 m / s, not yet reaching the starting threshold of 1.20 m / s. Combined with... Figure 6 It can be further seen that the velocity increment curve is below the 0.06m / s threshold line twice in the 1.2s and 1.6s endpoint intervals, which overlaps with the pressure drop rate exceeding the limit, thus triggering the trend judgment zone. After the system completes the main gas source switch at 1.6s, it immediately enters the recovery gas supply lock zone, and is not allowed to switch back to the recovery gas storage channel for gas supply until the starting threshold is reached at 3.2s.

[0096] To ensure stable gas supply after switching, this embodiment immediately sets the gas supply lock-up flag after switching the main gas source in advance, prohibiting switching back to the gas storage channel before the train speed reaches the starting threshold. Although the recovery pressure is still 0.54 MPa at 1.6s, which is higher than the lower limit of 0.40 MPa, the system maintains the main gas source supply until the train speed reaches 1.28 m / s. This avoids traction fluctuations caused by repeated switching between the recovery gas source and the main gas source, and also avoids the risk of secondary stall during the heavy-load start-up phase. Actual records show that the vehicle acceleration gradually recovers between 1.6s and 3.2s, and the train successfully passes through the most unfavorable section for the upward start-up. This process... Figure 5 The main performance was that after the main air source took over, the vehicle speed gradually increased from 0.33m / s to 1.28m / s, while the recovery pressure remained stable at around 0.54MPa. This indicates that although the system retained the remaining recovered air volume, it did not call up this part of the air source under the lock-up condition, thus ensuring the continuity and stability of subsequent traction.

[0097] This embodiment also calculates the effective output during the pressure-limited gas supply phase. The effective output power is evaluated using Equation 3.

[0098]

[0099] In the formula, This is the upper limit of gas supply. This represents the equivalent gas supply volumetric flow rate. Taking 0s to 1.6s as the gas recovery supply phase, and sampling flow rates of 0.041 m³ / s, 0.043 m³ / s, 0.045 m³ / s, and 0.047 m³ / s for four sampling intervals, then...

[0100]

[0101]

[0102] Assuming 1 MPa·m³ is equivalent to 1 MJ, the effective output is approximately 43.5 kJ. If pressure limiting is not applied and gas is supplied directly at the actual pressure, the simultaneous output is approximately 0.0484 MPa·m³, equivalent to about 48.4 kJ. Compared to the former, the output loss of pressure-limited gas supply is approximately 10.2%, but the initial peak supply pressure can be limited from 0.76 MPa to 0.62 MPa, equivalent to reducing the peak pressure by 0.14 MPa. Figure 7 As shown in the bar chart, within the four gas supply sampling intervals, the grouped bar charts for pressure-limited and unpressure-limited gas supply visually reflect the differences in output contribution between each interval. The first three intervals, constrained by the 0.62 MPa upper limit, have lower outputs than the unpressure-limited interval. In the fourth interval, since the actual pressure has dropped to 0.61 MPa, the outputs of both methods are equal. Therefore, it is evident that pressure-limited gas supply significantly improves start-up smoothness with only a loss of approximately 10.2% of effective output.

[0103] Regarding the maximum gas supply duration, the controller synchronously starts a 3.2s timer from 0s. In this implementation, the regenerative gas supply was switched ahead of schedule at 1.6s due to trend judgment, before reaching the maximum duration, but the upper limit logic remained effective. If there is no combined effect of insufficient speed increase and excessively rapid pressure drop during the start-up process, the system will also forcibly switch to the main gas source when 3.2s is reached. Even if the vehicle speed has not yet reached 1.20m / s, it will not continue to consume the compressed gas in the regenerative gas storage path, thus ensuring that the subsequent braking regeneration cycle still has a reasonable gas volume margin. The control logic in this embodiment does not simply rely on a certain threshold trigger, but rather uses the upper limit of gas supply, the rate of pressure drop, the speed increment trend, and the maximum gas supply duration to form a multi-condition constraint link, so that the regenerative gas is given priority for starting assistance, and the main gas source is switched in time after insufficient gas supply is detected, and repeated switching is avoided through a lock-up strategy.

Claims

1. An energy-saving control method for energy recovery in a pneumatic monorail, characterized in that... include: When a deceleration or stop command is received during operation, or when the vehicle speed is detected to exceed the preset limit, or when the vehicle speed is detected to be continuously increasing under downhill conditions and reaching the preset overspeed risk criterion, a deceleration requirement is generated. In response to the deceleration requirement, when the pressure in the recovery storage passage is lower than the preset upper limit, a command to connect the recovery storage passage is output, controlling the pneumatic drive unit to enter a state that can be reverse-driven by the load, so that the compressed gas generated by the reverse-driven process is introduced into the recovery storage passage for recovery; during the energy recovery braking state, the vehicle speed change is monitored, and if the vehicle speed does not decrease according to the preset deceleration rate or does not decrease to the target speed within the preset time, it is determined that the current braking force is insufficient. When the current braking force is determined to be insufficient, mechanical braking is engaged to supplement the braking force, and the recovery gas storage passage is kept open during the mechanical braking engagement so that the compressed gas generated by the reverse drag continues to be recovered; when the vehicle speed drops to the target speed or the parking conditions are met, the energy recovery braking is disengaged and the recovery gas storage passage is closed, and the vehicle switches to hold or parking control.

2. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 1, characterized in that, The connection of the gas recovery and storage passage adopts a single setting and pressure holding: after generating the deceleration demand, a connection command is output, and then the connection holding condition is that the recovery pressure in the gas recovery and storage passage reaches a preset holding threshold; when the recovery pressure is lower than the holding threshold, the gas recovery and storage passage is disconnected and the energy recovery braking state is exited.

3. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 1, characterized in that, When the pressure in the gas recovery passage reaches the preset upper limit and the deceleration requirement still exists, the gas recovery passage is closed, and the pneumatic drive unit enters the controlled back pressure damping state to provide braking force; if the braking force provided by the controlled back pressure damping is still insufficient, mechanical braking is triggered until the vehicle speed drops to the target speed or the stopping condition is met.

4. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 1, characterized in that, After the energy recovery braking is disengaged and the vehicle is put into hold or parking control, when a starting demand or upward traction demand occurs, the compressed gas in the recovery gas storage passage is used to supply air to the pneumatic drive unit; when the vehicle speed reaches the preset starting threshold or the pressure in the recovery gas storage passage drops to the preset lower limit, the main gas source is switched to supply air.

5. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 2, characterized in that, After the output of the connection command, a preset confirmation time limit is set. If the recovery pressure does not reach the preset holding threshold within the confirmation time limit, it is determined that recovery has not been established, the recovery gas storage passage is disconnected and the energy recovery braking state is exited.

6. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 2, characterized in that, The preset holding threshold adopts a hysteresis criterion, including a holding upper threshold and a releasing lower threshold; when the recovery pressure is higher than the holding upper threshold, the recovery gas storage passage is kept connected; when the recovery pressure is lower than the releasing lower threshold and continues for a preset holding time, the recovery gas storage passage is disconnected and the energy recovery braking state is exited.

7. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 4, characterized in that, The method of supplying compressed gas to the pneumatic drive unit using the gas recovery storage passage includes pressure-limited gas supply: when the pressure of the gas recovery storage passage is higher than the preset gas supply upper limit, the gas supply pressure is first limited to the gas supply upper limit before supplying gas to the pneumatic drive unit.

8. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 4, characterized in that, If insufficient speed increase and a pressure drop rate exceeding a preset value are detected before the vehicle speed reaches the preset starting threshold, the system will switch to supplying gas from the main gas source in advance.

9. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 4, characterized in that, The duration of gas supply through the gas recovery and storage channel does not exceed the preset maximum duration; when the maximum duration is reached, even if the vehicle speed has not reached the preset starting threshold, the gas supply will switch to the main gas source.

10. The energy-saving control method for energy recovery of a pneumatic monorail according to claim 8, characterized in that, The insufficient increase in vehicle speed is determined by trend judgment: the vehicle speed is sampled at least twice within a preset judgment window. If the vehicle speed increment is continuously lower than the preset minimum increment and the pressure drop rate of the gas recovery and storage passage exceeds the preset value, the system will switch to supply gas from the main gas source in advance, and will prohibit switching back to the gas recovery and storage passage before the vehicle speed reaches the preset starting threshold.

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