System and method for synchronously controlling temperatures of upper die and lower die of 3D cover plate glass
Technical Field
The invention belongs to the technical field of 3D cover plate glass temperature control, and particularly relates to a method for controlling the temperature synchronization of an upper die and a lower die of a 3D cover plate.
Background
With the wide application of wireless charging technology and flexible OLEDs, cover glass needs to be matched to be made into a curved surface shape, referred to as 3D cover glass in the industry. At present, 3D cover plate models are released by various mobile phone manufacturers, the 3D glass cover plate can be smoothly connected with the middle frame by 180 degrees, and the human engineering principle is better met, so that the hand feeling experience of the sliding screen is greatly improved. The glass material is better than metal and plastic materials in the aspects of electromagnetic shielding, machinability, aesthetic feeling and the like, and a mobile phone manufacturer also adopts 3D glass to replace a metal or plastic rear cover for the needs of product differentiation and wireless charging technology. The hot bending forming process is the mainstream forming process of the 3D glass at present.
The performance of the hot bending die material requires that the material has the characteristics of fine grains, compact and uniform structure, high thermal stability, easy processing, good heat conductivity coefficient, small thermal expansibility and the like. Alloy, ceramic and graphite can be generally selected, but the excellent characteristics of the graphite better meet the requirements of the 3D cover plate glass hot bending die, most of the graphite in the industry is used as a die raw material in order to improve the uniformity of products, and the graphite dies for 3D glass are generally used in pairs, namely matched with a concave-convex die.
The concave-convex mould of the graphite mould is independently controlled, but the problem of poor uniformity of the product is not effectively solved. The reason is that the heat flux density of each area is different, the temperature rise and the temperature fall asynchronously in the process of independently controlling the temperature of the concave-convex die, the temperature control of the concave-convex die is coupled mutually, and the phenomenon that the final temperature of a product generates continuous oscillation or the temperature difference of the concave-convex die is easily caused by the asynchronous temperature in the process.
The 3D glass hot bending forming process comprises the following steps:
a preheating stage: the original glass sheet is loaded into a graphite mould and then enters a preheating area, the mould is heated in the preheating area, the temperature of the glass is gradually raised after heat conduction of the mould, and the temperature is slowly and stably transited to a hot bending forming stage.
And (3) hot bending forming: after the glass enters the area, the temperature reaches the operation temperature, the glass deforms under the action of external force and finally conforms to the curvature of the mold, and the temperature setting is carried out in combination with the deformation point and the softening point of the glass at the stage.
And (3) annealing stage: the glass is relieved of residual stress in this region and temperature settings should be made in conjunction with the glass annealing point, strain point.
And (3) a cooling stage: under the effect of cooling device, glass cools off the design, and the temperature setting is set up according to the condition such as mould heat conduction, avoids glass warpage to exceed standard.
In the hot bending forming process, temperature and pressure are the most important control parameters, and the temperature and the pressure are slightly changed near a hot bending forming critical point, so that the hot bending forming is obviously changed, and if the temperature is set to be too low, glass is easy to be crushed due to the fact that the glass does not reach the deformation point temperature; the temperature of the upper mold and the lower mold of the mold is inconsistent, so that the heating rates of the upper surface and the lower surface of the glass are inconsistent, the glass is bent, and the glass is cracked under the stress state when the glass is serious. The research on the technology for synchronously controlling the temperature of the upper die and the lower die in the hot bending forming process has great significance for improving the forming yield and quality of the 3D cover plate glass.
The traditional upper and lower die temperature control structure is parallel control, namely the temperature target value of each region is the same, the upper and lower die temperatures are independently controlled, the temperature difference value parameter of the upper and lower die temperatures is not included in the algorithm processing, the temperature rise and fall speed rate between the regions is different, and the temperature surface temperature of the upper and lower dies is asynchronous.
Disclosure of Invention
In order to solve the technical problem, the invention provides a system and a method for synchronously controlling the temperature of an upper mold and a lower mold of a 3D cover plate colored glaze.
In order to solve the technical problems, the invention adopts the following technical scheme:
a temperature synchronous control system for upper and lower dies of a 3D cover plate colored glaze comprises an upper die main loop, an upper die auxiliary loop, a lower die main loop and a lower die auxiliary loop;
the upper die main loop is provided with an upper die main controller and an upper die heating wire, the upper die auxiliary loop is provided with an upper die auxiliary controller, the output ends of the upper die main controller and the upper die auxiliary controller are respectively connected with the input end of the upper die heating wire, the lower die main loop is provided with a lower die main controller and a lower die heating wire, the lower die auxiliary loop is provided with a lower die auxiliary controller, and the output ends of the lower die main controller and the lower die auxiliary controller are respectively connected with the input end of the lower die heating wire;
the difference between the output temperature of the upper die heating wire and the target set temperature of the die is used as the input regulating variable of the upper die main controller, the difference between the output temperature of the upper die heating wire and the output temperature of the lower die heating wire is used as the input regulating variable of the upper die sub-controller, and the output quantity of the upper die main controller and the output quantity of the upper die sub-controller are superposed and used as the input regulating variable of the upper die heating wire;
and the difference between the output temperature of the lower die heating wire and the target set temperature of the die is used as the input regulating quantity of the lower die main controller, the difference between the output temperature of the lower die heating wire and the output temperature of the upper die heating wire is used as the input regulating quantity of the lower die sub controller, and the output quantity of the lower die main controller and the output quantity of the lower die sub controller are superposed and used as the input regulating quantity of the lower die heating wire.
The upper die main controller, the upper die auxiliary controller, the lower die main controller and the lower die auxiliary controller are PID controllers.
A method for synchronously controlling the temperature of an upper mold and a lower mold of 3D cover glass comprises the following steps:
setting a target set temperature Sv (t) of the die, and detecting the output temperature of the upper die heating wire as vu(t), the output temperature of the lower die heating wire is recorded as vd(t);
Calculating each temperature difference
eu(t)=Sv(t)-vu(t),ed(t)=Sv(t)-vd(t),eud(t)=vu(t)-vd(t),edu(t)=vd(t)-vu(t),
U is obtained by calculationu(t)、ud(t)、uud(t)、udu(t) control amount, wherein uu(t) is the output of the control quantity of the upper die main loop, ud(t) output of control quantity of main loop of lower die, uud(t) is an upper dieOutput of the secondary loop during control udu(t) outputting the control quantity of the lower die secondary loop;
will uu(t)、uud(t) as the input control quantity of the upper die heating wire after superposition, ud(t)、uduAnd (t) after superposition, the control quantity is used as the input control quantity of the lower die heating wire.
Said u isu(t)、ud(t)、uud(t)、udu(t) the control quantity is controlled by a PID controller, and is calculated by adopting a PID control algorithm to obtain: the PID controller is composed of a proportional unit (P), an integral unit (I) and a differential unit (D), and the input e of the PID controller isu(t) and output udThe relationship of (t) is:
in the formula (I), the compound is shown in the specification,
respectively an error, an error integral and an error differential term;
kp,ki,kdproportional coefficient, integral coefficient, differential coefficient,
ud(t)=PID(ed(t))
uu(t)=PID(eu(t))
uud(t)=PID(eud(t))
udu(t)=PID(edu(t))。
the invention introduces a cross coupling structure, which not only controls the temperature of the upper die and the lower die heating wires independently, but also utilizes the temperature difference between the upper die heating wires and the lower die heating wires as a control input regulating quantity to effectively improve the synchronization performance of the temperature of the upper die and the temperature of the lower die, thereby ensuring the self control precision, simultaneously giving consideration to the temperature synchronization of the upper die and the lower die, realizing the effect of high-precision synchronous temperature control of the upper die and the lower die, improving the dynamic performance of the system in the temperature conversion process while not influencing the control precision of the system, solving the problem of the synchronization control and the precision of the upper die and the lower die of the 3D cover plate glass, and improving the quality and the yield of the formed 3D cover plate glass.
Drawings
FIG. 1 is a schematic diagram of the system connection of the present invention;
FIG. 2 is a schematic diagram of a cascade PID mold temperature control structure.
Detailed Description
For a better understanding of the features and technical means of the invention, together with the specific objects and functions attained by the invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
As shown in the attached figure 1, the invention discloses a temperature synchronous control system for upper and lower molds of a 3D cover plate colored glaze, which comprises an upper mold main loop, an upper mold auxiliary loop, a lower mold main loop and a lower mold auxiliary loop;
the upper die main loop is provided with an upper die main controller and an upper die heating wire, the upper die auxiliary loop is provided with an upper die auxiliary controller, the output ends of the upper die main controller and the upper die auxiliary controller are respectively connected with the input end of the upper die heating wire, the lower die main loop is provided with a lower die main controller and a lower die heating wire, the lower die auxiliary loop is provided with a lower die auxiliary controller, and the output ends of the lower die main controller and the lower die auxiliary controller are respectively connected with the input end of the lower die heating wire.
And the difference between the output temperature of the upper die heating wire and the target set temperature of the die is used as the input regulating quantity of the upper die main controller, the difference between the output temperature of the upper die heating wire and the output temperature of the lower die heating wire is used as the input regulating quantity of the upper die sub-controller, and the output quantity of the upper die main controller and the output quantity of the upper die sub-controller are superposed and jointly used as the input regulating quantity of the upper die heating wire.
And the difference between the output temperature of the lower die heating wire and the target set temperature of the die is used as the input regulating quantity of the lower die main controller, the difference between the output temperature of the lower die heating wire and the output temperature of the upper die heating wire is used as the input regulating quantity of the lower die sub controller, and the output quantity of the lower die main controller and the output quantity of the lower die sub controller are superposed and used as the input regulating quantity of the lower die heating wire.
The upper die main controller, the upper die auxiliary controller, the lower die main controller and the lower die auxiliary controller are PID controllers.
The output temperature of the upper die heating wire and the output temperature of the lower die heating wire are different, and then the obtained temperature deviation signal is used as a power compensation signal of the upper die heating wire and the lower die heating wire to adjust the power of the heating wires in real time, so that the temperature synchronization of the upper die and the lower die can be considered while the control precision of the upper die and the lower die is ensured, the effect of high-precision synchronous temperature control of the upper die and the lower die is realized, and the dynamic performance of the system in the temperature transition process is improved while the control precision of the system is not influenced.
A method for synchronously controlling the temperature of an upper mold and a lower mold of 3D cover glass comprises the following steps:
setting a target set temperature Sv (t) of the die, and detecting the output temperature of the upper die heating wire as vu(t), the output temperature of the lower die heating wire is recorded as vd(t);
Calculating each temperature difference
eu(t)=Sv(t)-vu(t),ed(t)=Sv(t)-vd(t),eud(t)=vu(t)-vd(t),edu(t)=vd(t)-vu(t),
U is obtained by calculationu(t)、ud(t)、uud(t)、udu(t) control amount, wherein uu(t) is the output of the control quantity of the upper die main loop, ud(t) output of control quantity of main loop of lower die, uud(t) is the output of the upper die auxiliary loop control, udu(t) outputting the control quantity of the lower die secondary loop;
will uu(t)、uud(t) as the input control quantity of the upper die heating wire after superposition, ud(t)、uduAnd (t) after superposition, the control quantity is used as the input control quantity of the lower die heating wire.
Said u isu(t)、ud(t)、uud(t)、udu(t) the control quantity is controlled by a PID controller, and is calculated by adopting a PID control algorithm to obtain: the PID controller is composed of a proportional unit (P), an integral unit (I) and a differential unit (D), and the input e of the PID controller isu(t) and output ud(t) ofThe relationship is as follows:
in the formula (I), the compound is shown in the specification,
respectively an error, an error integral and an error differential term;
kp,ki,kdproportional coefficient, integral coefficient, differential coefficient,
through the control quantity, the input quantity is adjusted, and the temperature synchronism of the upper die heating wire and the lower die heating wire is ensured, so that the heating temperatures of the upper die and the lower die are ensured.
As can be seen from the above, the control quantity output u of the upper die main loopu(t) and the lower die main loop control amount output ud(t), when the conventional error is adjusted, the auxiliary loop is used, the temperature of the upper die heating wire and the temperature of the lower die heating wire are subjected to difference value to adjust the input quantity, and therefore the problem that the upper die temperature and the lower die temperature are not synchronous due to the fact that the temperature rise of partial areas is too fast caused by uneven heat flow density can be effectively solved.
In the invention, the measured output temperature of the upper die heating wire and the measured output temperature of the lower die heating wire are respectively subjected to difference and used as input regulating quantity, and the cross coupling structure is adopted, so that the synchronism of the temperatures of the upper die and the lower die can be effectively improved.
In addition, in order to avoid steady-state oscillation of the system, the system adopts a control strategy of automatic switching of PID parameters in a partition area. A single PID parameter cannot be applied to the full temperature zone. According to debugging experience, the system divides the temperature interval into a low-temperature area, a medium-temperature area and a high-temperature area according to the temperature interval, and carries out debugging respectively according to the set value of the temperature and the actual value at the current moment, thereby selecting a proper PID parameter to achieve the effect of accurate temperature control. As shown in fig. 2, on the loop, through two PIDs, the temperature controlled output of the heating wire of the mold is v' (t), the temperature controlled output of the mold is v (t), the temperature controlled output of the mold is different from the target set temperature of the mold and is used as the input quantity of the first-stage PID, the temperature controlled output of the heating wire is different from the output quantity of the first-stage PID and is used as the input quantity of the second PID, and the output quantity u (t) of the second PID is used as the input quantity of the heating wire.
In addition, when the application is specifically implemented,
(1) sv (t) is set according to a 3D cover plate glass process, and PID parameters of a low-temperature area, a medium-temperature area and a high-temperature area are respectively set;
(2) the thermocouple sensors respectively measure the temperature v of the upper die and the lower die of the 3D cover plate glass formingd(t)、 vu(t);
(3) The following error values are calculated respectively,
eu(t)=Sv(t)-vu(t),ed(t)=Sv(t)-vd(t),eud(t)=vu(t)-vd(t),edu(t)=vd(t) -vu(t),
(4) calculating u by PID algorithm and cascade structureu(t)、ud(t)、uud(t)、udu(t) controlling the amount.
(5) And outputting the output value of the control quantity to the heating wires of the upper die and the lower die to realize the synchronous temperature control of the upper die and the lower die.
Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments or make equivalent substitutions for some technical features, but any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.