A temperature control method and system for a probe station

Abstract

This invention discloses a temperature control method and system for a probe station. The probe station includes a Stirling machine, a heater, and a pump, wherein the cold head of the Stirling machine is in contact with a hot plate. The method includes: acquiring the hot plate temperature and a target hot plate temperature; determining a temperature control mode based on the hot plate temperature and the target hot plate temperature; determining control constraints and control objectives that match the current control mode; determining an optimal control sequence for the Stirling machine frequency, heater power, and pump speed under the control constraints and control objectives; and using the optimal control sequence to control the hot plate temperature to gradually change to the target hot plate temperature.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology, and in particular to a temperature control method and system for a probe station. Background Technology

[0002] As a core device for performance testing of semiconductor chips, precision electronic components, and other devices, the probe station's temperature control accuracy directly determines the accuracy and reliability of the test data. In device testing scenarios, it is often necessary to simulate device performance under different operating conditions. Therefore, the probe station needs to achieve precise temperature control over a wide temperature range (such as -196℃ to 300℃) and adapt to various control requirements such as rapid temperature change, stable constant temperature, and disturbance rejection.

[0003] Existing probe stations require the use of a temperature control system. Current temperature control systems and methods suffer from the following drawbacks: Existing technologies often employ fixed-parameter PID control or simple fuzzy control, resulting in large temperature overshoot and severe fluctuations, failing to meet the constant temperature requirements of precision testing. Fixed-parameter control struggles to adapt to system parameter drift, easily leading to decreased temperature control accuracy and reduced stability. Summary of the Invention

[0004] The present invention provides a temperature control method and system for a probe station, in order to solve at least one defect existing in the prior art.

[0005] In a first aspect, embodiments of the present invention provide a temperature control method for a probe station, the probe station comprising a Stirling engine, a heater, and a pump, wherein the cold head of the Stirling engine is in contact with a hot plate, characterized in that it comprises:

[0006] The hot plate temperature and the target hot plate temperature are obtained, and the temperature control mode is determined based on the hot plate temperature and the target hot plate temperature.

[0007] Determine the control constraints and control objectives that match the current control mode, and determine the optimal control sequence for Stirling machine power, heater power, and pump speed under the control constraints and control objectives;

[0008] The optimal control sequence is used to control the temperature of the hot plate to gradually change to the target temperature of the hot plate.

[0009] Optionally, determining the optimal control sequence for Stirling machine power, heater power, and pump speed under the said control constraints and control objectives includes:

[0010] The temperature of the hot plate over the next N cycles is predicted using a system thermodynamic model. Based on the predicted trend, the optimal control sequence for Stirling machine power, heater power, and pump speed is determined under the control constraints and objectives.

[0011] After executing the first control quantity in the optimal control sequence, obtain the current hot plate temperature, and update the heat load disturbance term in the system thermodynamics model according to the current hot plate temperature and the predicted value of the temperature within the current cycle.

[0012] Optionally, the temperature control mode includes a first mode;

[0013] When |T_set - T_plate| > ΔT_fast, it is the first mode, where T_set represents the target hot plate temperature, T_plate represents the hot plate temperature, and ΔT_fast represents the first threshold;

[0014] The control constraints and control objectives under the first module include: if heating is required, the Stirling engine power is 0, the heater power is the maximum power, and the pump speed is the maximum speed; if cooling is required, the Stirling engine power is the maximum power and the heater power is 0.

[0015] Optionally, the temperature control mode includes a second mode;

[0016] When |T_set - T_plate| ≤ ΔT_fast and dΔT_fast / dt < k, it is the second mode, where T_set represents the target hot plate temperature, T_plate represents the hot plate temperature, ΔT_fast represents the first threshold, and k represents the second threshold;

[0017] The control constraints and control objectives under the second module include: the pump speed is a preset speed, and the preset speed is used to reduce the thermal noise and thermal fluctuations caused by fluid flow; the Stirling engine power is a preset power, and the preset power is used to offset the static heat load.

[0018] Optionally, the temperature control mode includes a third mode;

[0019] When the hot plate temperature suddenly changes and the change rate exceeds the third threshold, it is the third mode;

[0020] The control constraints and control objectives under the third mode include: performing step control on the Stirling engine power and the heater power, and the step control is used to compensate for the disturbance that causes the sudden change of the hot plate temperature.

[0021] Optionally, after determining the optimal control of the Stirling engine power, it further includes: performing vibration suppression on the Stirling engine power, and the vibration suppression is used to avoid Stirling engine resonance.

[0022] Optionally, performing vibration suppression on the Stirling engine power includes:

[0023] Determine the operating frequency and temperature point of the Stirling engine, and determine the vibration suppression control quantity by querying a preset vibration sensitivity table according to the operating frequency and temperature point.

[0024] Optionally, using a system thermodynamic model to predict the temperature of the hot plate over the next N cycles includes:

[0025] Using the hot plate temperature, outlet temperature, and cold head temperature of the previous cycle as the initial state, and combining the current Stirling machine power, heater power, pump speed, and heat load disturbance, the system thermodynamic model is used to predict the temperature of the hot plate in the next N cycles.

[0026] Optionally, determining the system thermodynamic model includes:

[0027] The Stirling engine and heater are controlled to cause the fluid temperature to change stepwise within a preset range. The total heat capacity of the system, the thermal resistance from the hot plate to the environment, and the heat transfer coefficient from the cold head to the fluid in the system thermodynamic model are identified by the response data of the hot plate temperature, the outlet temperature, and the cold head temperature.

[0028] Secondly, embodiments of the present invention provide a temperature control system for a probe station, wherein the system executes any of the temperature control methods described in the embodiments of the present invention.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. This invention proposes a temperature control method. In this method, temperature control modes are dynamically divided, and different modes are adjusted accordingly. This can avoid the problem of imbalance between accuracy and efficiency caused by using a set of parameters to adapt to all scenarios.

[0031] 2. In this method, based on the constraints and objectives of the current mode, the optimal control sequence for the Stirling machine frequency, heater power, and pump speed is calculated in real time. This sequence is dynamically updated according to changes in hot plate temperature, system parameter drift, and external disturbances. Since the optimal control sequence fully considers the nonlinearity and strong coupling characteristics of the temperature control system, it can adapt to changes in system state. Therefore, it can solve the problem that fixed parameter control is difficult to adapt to parameter drift and external disturbances, and can ensure that high temperature control accuracy is maintained during long-term operation. Attached Figure Description

[0032] Figure 1 This is a flowchart of the temperature control method in the embodiment. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0034] Example 1

[0035] This embodiment proposes a temperature control method for a probe station. The probe station includes a refrigeration system, which includes a Stirling engine, heat pipes, transfer hoses, heaters, controllers, pumps, temperature sensors, and a control box.

[0036] The Stirling compressor consists of a variable frequency drive (VFD) main unit and a cold head. The cold head contacts the cold stage (hot plate) at one end via heat pipes. VFD control (frequency adjustment) allows for changes in cooling output and the Stirling compressor's own temperature. This protects the heat pipes and the installation layout of compatible equipment, preventing installation interference caused by hard connections, reducing cooling loss, and ensuring smooth refrigerant circulation within the heat pipes. Heaters are positioned near the probe station, cold stage, or hot plate to precisely compensate for cooling deviations, working in conjunction with the Stirling compressor to achieve high-precision temperature control. A pump regulates the refrigerant flow efficiency within the heat pipes. Temperature sensors collect data on the hot plate temperature (T_plate), heat pipe outlet temperature (T_out), Stirling compressor cold head temperature (T_c), and the actual temperature of the probe station's cold stage, providing real-time feedback for control.

[0037] In this solution, the controller is configured to execute the temperature control method proposed in this embodiment. The control box integrates the hardware carrier of the controller, power module, and signal processing circuit, providing a stable operating environment and facilitating installation and maintenance.

[0038] In this scheme, the cold stage of the probe station directly supports the components of the test sample and is in contact with the other end of the heat pipe. The cooling effect is achieved through the heat pipe, and the ultimate goal is to stabilize the sample temperature at the set value (T_set) to meet the temperature requirements of the test process.

[0039] After the Stirling machine starts, the temperature of the cold head drops rapidly, contacting one end of the heat pipe and absorbing heat from the refrigerant inside. The refrigerant condenses from a gaseous state to a liquid state at the cold head. Under the influence of gravity or capillary force, the liquid refrigerant flows through the transfer hose to the other end of the heat pipe inside the probe stage's cold stage, absorbing heat from the cold stage and the sample, and rapidly vaporizing back into a gaseous state, thus cooling the cold stage. The gaseous refrigerant flows back to the Stirling machine's cold head, where it is condensed back into a liquid state, forming a closed-loop refrigeration cycle that continuously provides cooling to the cold stage.

[0040] Figure 1 This is a flowchart of the temperature control method in the embodiment, for reference. Figure 1 The methods include:

[0041] S101. Obtain the hot plate temperature and the target hot plate temperature, and determine the temperature control mode based on the hot plate temperature and the target hot plate temperature.

[0042] S102. Determine the control constraints and control objectives that match the current control mode, and determine the optimal control sequence for the Stirling machine frequency, heater power, and pump speed under the control constraints and control objectives.

[0043] Combining steps S101 and S102, this solution utilizes a differentiated set of temperature control strategies based on the difference between the current temperature state of the hot plate and the target temperature requirement, allowing for more targeted control actions. For example, the temperature control modes may include rapid temperature change mode, high-precision steady-state mode, and dynamic disturbance rejection mode.

[0044] For example, in this solution, under the rapid temperature change mode, the control constraints may include: Stirling machine frequency range of 30~70Hz, frequency change Δf ≤ 5Hz between adjacent cycles (to avoid resonance), and the highest frequency not exceeding the equipment's rated value; heater power range of 0~100% of rated power, power change ΔP ≤ 10W / s between adjacent cycles; pump speed range of 1500~3000rpm, and the highest speed ≤ 3000rpm.

[0045] Control objectives may include: First objective (weight 0.8): maximize the rate of temperature change (heating / cooling rate) to quickly approach T_set; Second objective (weight 0.2): avoid overload of actuators and ensure equipment safety.

[0046] For example, in this solution, under high-precision steady-state mode, the control constraints may include: Stirling machine frequency range of 35~60Hz, frequency change Δf ≤ 2Hz between adjacent cycles; heater power range of 0~20% of rated power, supporting PWM pulse width modulation; pump speed fixed at 1500~2000rpm.

[0047] The control objectives may include: the first objective (weight 0.9), achieving a temperature control accuracy of ±0.01~0.1℃ with no significant fluctuations; and the second objective (weight 0.1), minimizing energy consumption and reducing operating costs.

[0048] For example, in this scheme, under dynamic disturbance rejection mode, the control constraints may include: Stirling machine frequency change Δf ≤ 8Hz, and the final frequency does not exceed the 30~70Hz range; heater power change ΔP ≤ 20W / s, and the maximum power does not exceed the rated value; the pump speed maintains the current mode speed.

[0049] The control objectives may include: the first objective (weight 0.95), which is to suppress disturbances within 0.5s and control the temperature deviation within ±0.5℃; and the second objective (weight 0.05), which is to prevent secondary overshoot after disturbance suppression.

[0050] For example, in this scheme, the optimal control sequence of Stirling machine frequency, heater power and pump speed can be determined using the Model Predictive Control (MPC) algorithm.

[0051] For example, in this scheme, the current T_plate, T_set, and control quantity of the previous cycle can be used as inputs to MPC, and the future temperature can be predicted based on linear fitting; the objective function is established with the current control objective as the optimization direction and the control constraints as the boundary; the objective function is solved to obtain the control quantity (optimal control sequence) for the next 5 cycles, and only the control quantity of the first cycle is executed, and the solution is repeated in the next cycle.

[0052] S103. Use the optimal control sequence to control the hot plate temperature to gradually change to the target hot plate temperature.

[0053] In this solution, by adjusting the frequency of the Stirling engine, the temperature and cooling output of the cold head can be changed. When the frequency increases, the cold head temperature is lower and the cooling output is greater. The refrigerant phase change rate in the heat pipe is faster and the pressure is lower, thus enhancing the cooling capacity of the cold platform and lowering the temperature. When the frequency decreases, the cooling output decreases and the temperature of the cold platform increases.

[0054] In this solution, by adjusting the power of the heater, minor heat leakage or excess cooling can be offset, and the temperature can be stabilized within the target value ±0.1℃ (or higher precision).

[0055] In this solution, increasing the pump speed can accelerate the refrigerant circulation within the heat pipe and improve heat transfer efficiency; decreasing the pump speed can reduce thermal noise caused by fluid flow and ensure temperature stability.

[0056] This embodiment proposes a temperature control method applied to the temperature control of a probe station. This method dynamically divides temperature control modes and performs differentiated regulation for different modes, avoiding the accuracy and efficiency imbalance caused by using a single set of parameters to suit all scenarios. Based on the constraints and objectives of the current mode, the optimal control sequence for the Stirling machine frequency, heater power, and pump speed is calculated in real time, and this sequence is dynamically updated according to changes in hot plate temperature, system parameter drift, and external disturbances. Since the optimal control sequence fully considers the nonlinearity and strong coupling characteristics of the temperature control system, it can adapt to changes in system state, thus solving the problem of fixed parameter control's difficulty in adapting to parameter drift and external disturbances, ensuring high temperature control accuracy during long-term operation.

[0057] Based on any of the aforementioned schemes, in one possible implementation, determining the optimal control sequence for Stirling machine power, heater power, and pump speed under control constraints and control objectives includes:

[0058] The system thermodynamic model is used to predict the temperature of the hot plate over the next N cycles. Based on the changing trend, the optimal control sequence of Stirling machine frequency, heater power and pump speed is determined under control constraints and control objectives.

[0059] After executing the first control variable in the optimal control sequence, the current hot plate temperature is obtained, and the thermal load disturbance term in the system thermodynamic model is updated based on the current hot plate temperature and the predicted temperature in the current period.

[0060] In this scheme, the system thermodynamic model is used to predict the temperature of the hot plate in the next N cycles. This includes using the hot plate temperature, outlet temperature and cold head temperature of the previous cycle as the initial state, and combining the current Stirling machine power, heater power, pump speed and heat load disturbance, to predict the temperature of the hot plate in the next N cycles using the system thermodynamic model.

[0061] In this scheme, the thermal load disturbance term (Q_load) is a parameter in the system thermodynamic model. By dynamically adjusting the thermal load disturbance through the error between the actual temperature and the predicted value, the model can better fit the real-time operating conditions and ensure control robustness.

[0062] In this scheme, the heat load disturbance term Q_load is the real-time equivalent heat load disturbance of the system. Its sign and magnitude represent the direction and intensity of the disturbance: positive Q_load indicates that there is an additional heat absorption disturbance in the system, which will cause the actual temperature to be higher than the predicted value; negative Q_load indicates that there is an additional heat release disturbance in the system, which will cause the actual temperature to be lower than the predicted value; Q_load of 0 indicates that there is no additional disturbance, and the system thermodynamic model prediction is consistent with the actual operating conditions.

[0063] For example, in this scheme, Q_load is updated through an error correction model, which can be:

[0064] Q_load=[(T_plate_actual(1)-T_plate(0))×C / Δt]-(Q_heater(0)-P_stirling(0))

[0065] In the formula, T_plate_actual(1) represents the actual temperature, T_plate(0) represents the temperature prediction value, that is, the temperature in the 0th cycle predicted by the system thermodynamic model, Q_heater(0) and P_stirling(0) represent the Stirling machine power and heater power corresponding to the first Stirling machine frequency in the optimal control sequence, respectively, C represents the total heat capacity of the system, and Δt represents the control period.

[0066] In this scheme, the equivalent heat load causing the error is calculated by using the error between the actual temperature and the predicted value, which can avoid control oscillations caused by sudden disturbances. When updating Q_load, no complex model reconstruction is required; uncertainties such as environmental heat leakage and load fluctuations can be offset by simple error calculation, thus improving the accuracy of the system thermodynamic model and the robustness of control.

[0067] Based on any of the aforementioned schemes, in one possible implementation, the temperature control mode includes a first mode; when |T_set - T_plate| > △T_fast, it is the first mode, where T_set represents the target temperature of the hot plate, T_plate represents the temperature of the hot plate, and △T_fast represents the first threshold.

[0068] The control constraints and control objectives under the first module include: if heating is required, the Stirling machine power is 0, the heater power is at maximum power, and the pump speed is at maximum speed; if cooling is required, the Stirling machine power is at maximum power, and the heater power is 0.

[0069] In this scheme, the first mode is defined by the absolute deviation between the target temperature and the actual temperature. When |T_set - T_plate| > △T_fast, the first mode is triggered. The core objective of the first mode is to maximize the temperature change rate and minimize the temperature difference as quickly as possible.

[0070] In this scheme, the control constraints and control objectives are equivalent in both heating and cooling scenarios. In the heating scenario, the Stirling engine power is 0, cooling is stopped to prevent cold energy from offsetting heat; the heater power is at maximum power to maximize heating; and the pump speed is at maximum speed to maximize heat transfer efficiency, allowing the heater's heat to be quickly transferred to the hot plate. In the cooling scenario, the Stirling engine power is at maximum power to maximize cooling; the heater power is 0, heating is stopped to prevent heat from offsetting cooling; and the pump speed is at maximum speed to maximize heat transfer efficiency, allowing the Stirling engine's cold energy to be quickly transferred to the hot plate.

[0071] For example, in this solution, taking a heating scenario as an example, T_plate<T_set,|T_set-T_plate|> At 5℃, the Stirling machine frequency P_stirling(k), heater power P_heater(k), and pump speed V_pump(k) (k=1~5) for the next 5 cycles are determined using the MPC algorithm.

[0072] The constraints can be: Q_stirling(k) = 0 (Stirling machine power 0); P_stirling(k) ≥ 30Hz (minimum safe operating frequency), which must eventually stabilize at 30Hz; P_stirling adjacent period Δf ≤ 5Hz; P_heater(k) ≤ 50W (maximum power limit), which must eventually stabilize at 50W; V_pump(k) ≤ 3000rpm (maximum speed limit), which must eventually stabilize at 3000rpm; maximize the temperature change rate, dT / dt ≥ 1.8℃ / s; P_heater adjacent period ΔP ≤ 10W; V_pump adjacent period ΔV ≤ 300rpm.

[0073] The objective function can be: J = 0.9×J1 + 0.1×J2. J1 is the first objective, indicating the minimum sum of temperature differences in the next 5 cycles. J1 = Σ|T_set - T_plate(k)| (k = 1~5), the smaller it is, the faster the temperature rises; J2 is the second objective, indicating the minimum total energy consumption in the next 5 cycles. J2 = Σ[P_heater(k) + 0.5×V_pump(k) / 1000] (k = 1~5), the smaller it is, the more energy-efficient.

[0074] In this solution, the power of the Stirling engine is 0, and the frequency of the Stirling engine can be non-zero. Maintaining the Stirling engine frequency at a low frequency can reduce the start-stop loss. Also, when switching modes, the frequency can be quickly adjusted to the preset frequency. Adjusting the frequency gradually to 30 Hz to make the power 0 is smoother and causes less vibration than directly dropping to 0 Hz, making it easier to achieve the optimization goal.

[0075] Based on any of the above solutions, in an implementable manner, the temperature control mode includes a second mode; when 丨T_set - T_plate丨 ≤ △T_fast and d△T / dt < k, it is the second mode, where T_set represents the target temperature of the hot plate, T_plate represents the temperature of the hot plate, △T_fast represents the first threshold, k represents the second threshold, and △T = 丨T_set - T_plate丨.

[0076] The control constraints and control objectives under the second mode include: the pump speed is the preset speed, and the preset speed is used to reduce the thermal noise and thermal fluctuations caused by fluid flow; the power of the Stirling engine is the preset power, and the preset power is used to offset the static thermal load.

[0077] In this solution, the role of the second mode is to achieve fluctuation-free and high-precision temperature control by fixing the preset parameters and precise fine-tuning after the hot plate temperature approaches the target value. When |T_set - T_plate| ≤ △T_fast, it means the temperature has approached the target value and there is no need for rapid temperature change; when dT / dt < k, it means the temperature change is gentle and there are no large fluctuations, providing a basis for stable temperature control. The second mode is triggered only when both of the above conditions are met.

[0078] The core objective of the second mode is to minimize temperature fluctuations and suppress thermal noise to achieve high-precision steady-state temperature control. The pump speed under the second mode: is fixed at the preset speed (V_steady), and the core objective is to reduce the thermal noise and thermal fluctuations caused by fluid flow. Too fast pump speed will cause fluid disturbance, which is transmitted to the hot plate and causes temperature jitter; too slow pump speed will lead to uneven heat transfer. The preset speed is the optimal balance between uniform heat transfer and low disturbance; the power of the Stirling engine is fixed at the preset power (Q_stirling_base), and the core objective is to offset the static thermal load so that the hot plate temperature does not drift due to static loss.

[0079] For example, in this scheme, the MPC algorithm is used to determine P_stirling(k), P_heater(k), and V_pump(k) (k=1~5) for the next 5 periods.

[0080] The constraints can be: 42Hz≤P_stirling(k)≤48Hz (preset power range, to offset static heat load); 0W≤P_heater(k)≤10W; V_pump(k)=2000rpm; |T_plate(k)-T_set|≤0.02℃; |P_stirling(k)-P_stirling(k-1)|≤2Hz (k≥2); P_stirling(k)>44Hz, P_heater(k)≤5W; P_heater(k)>5W, P_stirling(k)≤44Hz.

[0081] The objective function can be: J = 0.8 × J1 + 0.2 × J2. J1 is the first objective, representing the sum of squares of the deviations between the hot plate temperature and T_set over the next 5 cycles, J1 = Σ[T_plate(k) - T_set]² (k = 1~5), the smaller the value, the more accurate the result; J2 is the second objective, representing the total energy consumption over the next 5 cycles, J2 = Σ[Q_stirling(k) + 2 × P_heater(k)] (k = 1~5), the smaller the value, the more energy-efficient the result.

[0082] Based on any of the aforementioned schemes, in one possible implementation, the temperature control mode includes a third mode; when the hot plate temperature undergoes a sudden change and the rate of change exceeds a third threshold, it is the third mode.

[0083] The control constraints and objectives in the third mode include: step control of the Stirling machine power and the heater power, which is used to compensate for disturbances that cause sudden changes in the hot plate temperature.

[0084] In this scheme, the third mode is used to quickly suppress sudden temperature changes in the hot plate (such as probe card contact heating, ambient airflow impact, sudden equipment failure, etc.) to avoid the temperature difference from increasing and affecting the subsequent temperature control accuracy.

[0085] For example, in this scheme, the control constraints may include: the Stirling machine power and heater power are only allowed to have a single step change. The control objectives may include: a first objective, to suppress disturbances within 0.5s and bring the temperature deviation back within ±0.5℃; and a second objective, to prevent secondary overshoot after disturbance suppression and avoid triggering new disturbances.

[0086] For example, in this scheme, the MPC algorithm is used to determine P_stirling(k) and P_heater(k) (k=1~5) for the next 5 periods.

[0087] Control constraints may include: when k=1, it is step control, |P_stirling(1)-P_stirling(0)|≤15Hz, |P_heater(1)-P_heater(0)|≤15W; when k≥2, |P_stirling(k)-P_stirling(k-1)|≤2Hz, |P_heater(k)-P_heater(k-1)|≤1W. 30Hz≤P_stirling(k)≤70Hz, 0W≤P_heater(k)≤50W.

[0088] The objective function can be: J = 0.95 × J1 + 0.1 × J2. J1 = |T_plate(5) - T_set| (the deviation is the smallest when k = 5), the smaller the value, the more accurate the result; J2 = Σ[P_stirling(k) + P_heater(k)] + 0.5 × Σ|ΔP_stirling(k)|, the smaller the value of J2, the more energy-efficient the result.

[0089] Based on any of the aforementioned schemes, in one possible implementation, after determining the optimal control of the Stirling machine frequency, the method further includes: vibration suppression of the Stirling machine frequency, the vibration suppression being used to avoid Stirling machine resonance.

[0090] In this scheme, after determining the optimal frequency control of the Stirling machine under the specified mode, a vibration suppression component is added. By avoiding the resonant frequency range of the Stirling machine and smoothing the power change rhythm, the risk of resonance is eliminated and mechanical wear of the equipment is avoided without changing the optimal frequency control objective.

[0091] For example, in this solution, vibration suppression of the Stirling machine frequency can specifically include:

[0092] For the optimal Stirling machine frequency sequence (represented by frequency f(k), k=1~M) for the next M cycles obtained from the first, second and third modes, determine whether f(k) of each cycle falls within the avoidance interval [f_res_low-Δf_safe, f_res_high+Δf_safe], where f_res_low represents the lower limit, f_res_high represents the upper limit, and Δf_safe represents the allowable deviation; calculate Δf(k)=|f(k)-f(k-1)| for adjacent cycles and determine whether it exceeds Δf_max of the corresponding mode.

[0093] If all f(k) avoid the avoidance interval and Δf(k)≤Δf_max, then execute directly; if individual f(k) falls into the avoidance interval or Δf(k) slightly exceeds the threshold, f(k) needs to be adjusted to avoid the avoidance interval; if multiple consecutive periodic f(k) fall into the avoidance interval, the optimal Stirling machine frequency sequence needs to be recalculated.

[0094] Based on any of the aforementioned schemes, in one possible implementation, vibration suppression of the Stirling machine power includes: determining the operating frequency and temperature point of the Stirling machine, and determining the vibration suppression control amount by querying a preset vibration sensitivity table based on the operating frequency and temperature point.

[0095] In this solution, a vibration sensitivity table is established in advance through offline testing. During actual operation, the current operating frequency of the Stirling machine and the temperature of the hot plate are collected in real time. The vibration sensitivity table is quickly queried to obtain the matching suppression control value, which is then sent to the actuator to achieve vibration suppression.

[0096] For example, in this solution, the vibration sensitivity meter can be determined in the following way:

[0097] Determine the operating frequency range of the Stirling machine and the temperature range of the hot plate, and set the suppression control value to the frequency fine-tuning value. Connect the Stirling machine to the test bench, connect the hot plate to the temperature controller, and install a piezoelectric vibration sensor at the connection point between the Stirling machine housing and the hot plate.

[0098] Fix one hot plate temperature point (e.g., -55℃), gradually increase the Stirling machine frequency from 30Hz to 70Hz, and record 3 sets of data every 1Hz of stabilization: current frequency f, vibration acceleration a, and frequency fine-tuning amount Δf to be applied; switch the hot plate temperature point in sequence according to the temperature step size to complete the test of all frequency-temperature combinations.

[0099] All test data were organized into a vibration sensitivity table, formatted as temperature point, operating frequency, and vibration suppression control value (Δf).

[0100] Based on any of the aforementioned schemes, in one possible implementation, determining the system thermodynamic model includes:

[0101] By controlling the Stirling engine and heater, the fluid temperature is made to change stepwise within a preset range. By using the response data of hot plate temperature, outlet temperature and cold head temperature, the total heat capacity of the system, the thermal resistance from the hot plate to the environment and the heat transfer coefficient from the cold head to the fluid in the system thermodynamic model are identified.

[0102] In this scheme, the total heat capacity C of the system (including hot plates, circulating fluid, connectors, etc.) characterizes the system's ability to store heat, with the unit being J / ℃. The larger the value, the slower the system temperature changes, and it determines the temperature response speed.

[0103] The thermal resistance R_amb between the hot plate and the environment characterizes the degree of heat transfer obstruction between the hot plate and the external environment, with the unit being °C / W; the larger the value, the smaller the heat loss and the better the system's thermal insulation performance.

[0104] The heat transfer coefficient K_stirling from the cold head to the fluid characterizes the intensity of heat exchange between the Stirling machine's cold head and the circulating fluid, with units of W / ℃. The higher the value, the higher the refrigeration / heat exchange efficiency, and the more obvious the cold head's control over the fluid temperature.

[0105] For example, in this scheme, the system thermodynamic model can be:

[0106]

[0107] In the formula, T_plate represents the hot plate temperature, Q_heat represents the heat generated by the heater, Q_cool represents the cooling capacity of the Stirling machine, Q_pump represents the heat generated by the pump, Q_loss represents the system heat loss, Q_load represents the heat load disturbance, Δt represents the control cycle, C represents the total heat capacity of the system, η_heat is the heater efficiency, K_stirling is the heat transfer coefficient from the Stirling machine cold head to the fluid, K_pump is the pump heat transfer coefficient, and R_amb is the thermal resistance from the hot plate to the environment.

[0108] In this scheme, real-time response data of hot plate temperature T_plate, outlet temperature T_out, and cold head temperature T_c are collected simultaneously. Based on the system thermodynamic model, a system identification algorithm (e.g., recursive least squares method) is used to fit the response data and model output, and finally the estimation of the three key parameters is achieved.

[0109] For example, in this solution, a total of 3 sets of step operating conditions are designed, covering heating, cooling and steady-state scenarios. Each set of operating conditions lasts for 10 sampling cycles. The controller alternately adjusts the heater and Stirling machine to achieve small step changes in fluid temperature and collect response data simultaneously.

[0110] After linearizing the system thermodynamic model, the collected response data is fed into the linearized model, and the total system heat capacity, thermal resistance from the hot plate to the environment, and heat transfer coefficient from the cold head to the fluid are identified by recursive least squares method.

[0111] In this scheme, the Stirling engine and heater are precisely controlled by the controller, so that the temperature of the circulating fluid changes stepwise within a preset small range. This avoids large fluctuations that could affect system stability, while fully stimulating the system's thermal dynamic response and providing effective data for identification.

[0112] Example 2

[0113] This embodiment proposes a temperature control system for a probe station. The system includes a controller, which is configured to execute any of the temperature control methods described in Embodiment 1. The implementation process and beneficial effects of the method are the same as the corresponding content described in Embodiment 1, and the specific details will not be described in detail here.

[0114] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A temperature control method for a probe station, the probe station comprising a Stirling engine, a heater, and a pump, wherein the cold head of the Stirling engine is in contact with a hot plate, characterized in that, Including: Obtain the hot plate temperature and the hot plate target temperature, and determine the temperature control mode according to the hot plate temperature and the hot plate target temperature; Determine the control constraints and control objectives matching the current control mode, and determine the optimal control sequence of the Stirling machine frequency, heater power and pump speed under the control constraints and control objectives; Use the optimal control sequence to control the hot plate temperature to gradually change to the hot plate target temperature.

2. The temperature control method for a probe station as described in claim 1, characterized in that, Determining the optimal control sequence of the Stirling machine frequency, heater power and pump speed under the control constraints and control objectives includes: Predict the temperature of the hot plate in the next N cycles by using the system thermodynamics model, and determine the optimal control sequence of the Stirling machine frequency, heater power and pump speed based on the change trend under the control constraints and control objectives; After executing the first control quantity in the optimal control sequence, obtain the current hot plate temperature, and update the heat load disturbance term in the system thermodynamics model according to the current hot plate temperature and the predicted value of the temperature in the current cycle.

3. The temperature control method for a probe station as described in claim 1, characterized in that, The temperature control mode includes the first mode; When |T_set - T_plate| > ΔT_fast, it is the first mode, where T_set represents the hot plate target temperature, T_plate represents the hot plate temperature, and ΔT_fast represents the first threshold; The control constraints and control objectives under the first mode include: if heating is required, the Stirling machine power is 0, the heater power is the maximum power, and the pump speed is the maximum speed; if cooling is required, the Stirling machine power is the maximum power and the heater power is 0.

4. The temperature control method for a probe station as described in claim 1, characterized in that, The temperature control mode includes the second mode; When |T_set - T_plate| ≤ ΔT_fast and dΔT / dt < k, it is the second mode, where T_set represents the hot plate target temperature, T_plate represents the hot plate temperature, ΔT_fast represents the first threshold, and k represents the second threshold; The control constraints and control objectives under the second mode include: the pump speed is the preset speed, and the preset speed is used to reduce the thermal noise and thermal fluctuations caused by fluid flow; the Stirling machine power is the preset power, and the preset power is used to offset the static heat load.

5. The temperature control method for a probe station as described in claim 1, characterized in that, The temperature control mode includes the third mode; When the hot plate temperature suddenly changes and the change rate exceeds the third threshold, it is the third mode; The control constraints and control objectives under the third mode include: performing step control on the Stirling machine power and the heater power, and the step control is used to compensate for the disturbance causing the sudden change of the hot plate temperature.

6. The temperature control method for a probe station as described in claim 1, characterized in that, After determining the optimal control of the Stirling machine frequency, vibration suppression of the Stirling machine frequency is further included, and the vibration suppression is used to avoid Stirling machine resonance.

7. The temperature control method for a probe station as described in claim 6, characterized in that, Vibration suppression of the Stirling machine frequency includes: Determine the working frequency and temperature point of the Stirling machine, and determine the vibration suppression control quantity by querying a preset vibration sensitivity table according to the working frequency and temperature point.

8. The temperature control method for a probe station as described in claim 2, characterized in that, Predicting the temperature of the hot plate in the next N cycles by using the system thermodynamics model includes: Using the hot plate temperature, outlet temperature, and cold head temperature of the previous cycle as the initial state, and combining the current Stirling machine frequency, heater power, pump speed, and heat load disturbance, the system thermodynamic model is used to predict the temperature of the hot plate in the next N cycles.

9. The temperature control method for a probe station as described in claim 2, characterized in that, Determining the thermodynamic model of the system includes: The Stirling engine and heater are controlled to cause the fluid temperature to change stepwise within a preset range. The total heat capacity of the system, the thermal resistance from the hot plate to the environment, and the heat transfer coefficient from the cold head to the fluid in the system thermodynamic model are identified by the response data of the hot plate temperature, the outlet temperature, and the cold head temperature.

10. A temperature control system for a probe station, characterized in that, The system performs the temperature control method according to any one of claims 1 to 9.

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