Temperature Feedback Control System Research Articles

Temperature Control Performance of a Built-In Motor Spindle by Developed Temperature Feedback Control System

The temperature control performance of a developed temperature feedback control system was experimentally investigated. The control system was based on a real-time temperature control of a cooling fluid. In particular, this study focused on the temperature control performance of a built-in motor spindle that used the developed temperature fedback control system. The built-in motor used in the study had water cooling jackets. The temperature of the built-in motor spindle was measured and feedback into the developed temperature feedback control system. Temperature control accuracy of the built-in motor spindle under steady state was then assessed. Furthermore, the effects of the time-variant changes in spindle rotation and ambient temperature on the performance of the temperature control system was investigated. The results of the experiments show that the temperature control accuracy of the built-in motor spindle under steady state condition was ±0.03°C. The temperature control performance of the built-in motor spindle under changes in the rotational speed of the spindle was examined. The experimental results show that the temperature change of the spindle could be suppressed to a maximum of approximately 0.3°C under transient state during sudden change in spindle speed. In addition, the effects of the changes in ambient and cooling water temperatures, which simulated actual environmental operating conditions, on the spindle temperature were investigated. The results show that the change in the spindle temperature could be suppressed by approximately less than ±0.1°C. These experimental results indicate that the developed temperature feedback control system achieved high temperature control accuracy and high response for the built-in motor spindle. In particular, the developed control system successfully controlled the time-variant change in the generated heat, thereby improving the thermal stability of the machine tool spindle.

Flapping actuation using temperature feedback control of coated shape memory alloy actuators

Shape memory alloys (SMAs) have been considered as actuators for micro application due to its high strength to weight ratio. Although it is mostly considered for linear or rotary actuation, in this study a technique using a temperature feedback control system has been proposed to produce oscillation at steady state suitable for flapping wing actuation in micro air vehicles (MAVs). A proportional-integral-derivative (PID) controller was used in the temperature feedback system to tune the frequency of oscillation of the shape memory alloy actuator. This system is compact as the oscillation can be produced without using components to translate from linear to rotary motion. Another challenge to be addressed is the slow cooling rate of the SMA actuator that occurs through natural convection resulting in slower flapping actuation. Thus, a viable approach to improve the actuation response is by coating the SMA to reduce hysteresis. An experimental study was conducted to evaluate the effects of heat convection on the SMA actuator's control performance by using SMA wire coated with silicone rubber. Its actuation was compared to the uncoated SMA wire to establish the effects of heat convection on SMA actuation behaviour. The response of the temperature feedback system of the SMA actuator for the flapping actuation under wind loading was evaluated using wind tunnel testing. The experimental results show that coated SMA wire resulted in increased actuation frequency. However, this effect became negligible as the airflow provided sufficient cooling and resulted in higher flapping frequency at Reynolds number greater than 7.5 × 103. Wind tunnel testing demonstrated that shape memory alloy actuators using a PID based temperature feedback control system may be used to produce flapping actuation at low Reynolds numbers.

Microwave-assisted fast and efficient dissolution of silkworm silk for constructing fibroin-based biomaterials

A microwave-assisted method was developed for extraction of water-soluble fibroin from silkworm silk. In order to explore enhancing effect of microwave, dissolution profiles of silk fibroin were monitored by protein concentration measurements, showing a faster extraction rate of the microwave-assisted method compared to the conventional methods. Meanwhile, characterization of the resultant silk fibroin regenerated by the microwave-assisted method indicated similarity to that by the conventional methods in that they exhibited similar molecular weight ranges, secondary structures and gelation capabilities. In contrast to traditional microwave-assisted methods, this study employed a laboratory microwave reactor equipped with a feedback temperature control system, which enabled easy control and maintenance of certain reaction temperature and temperature distribution. In this way, the present study, to an extent, resolved possible concerns that uncontrollable extreme high temperature under microwave would cause degradation of the silk fibroin chain. This new microwave-assisted method has demonstrated its advantages of significant reduction in time-consuming and energy cost, and thus stands for a promising economical and efficient method for regeneration of silkworm silk fibroin.

Design of a temperature measurement and feedback control system based on an improved magnetic nanoparticle thermometer

Magnetic fluid hyperthermia, as a novel cancer treatment, requires precise temperature control at 315 K–319 K (42 °C–46 °C). However, the traditional temperature measurement method cannot obtain the real-time temperature in vivo, resulting in a lack of temperature feedback during the heating process. In this study, the feasibility of temperature measurement and feedback control using magnetic nanoparticles is proposed and demonstrated. This technique could be applied in hyperthermia. Specifically, the triangular-wave temperature measurement method is improved by reconstructing the original magnetization response of magnetic nanoparticles based on a digital phase-sensitive detection algorithm. The standard deviation of the temperature in the magnetic nanoparticle thermometer is about 0.1256 K. In experiments, the temperature fluctuation of the temperature measurement and feedback control system using magnetic nanoparticles is less than 0.5 K at the expected temperature of 315 K. This shows the feasibility of the temperature measurement method for temperature control. The method provides a new solution for temperature measurement and feedback control in hyperthermia.

Novel hyperthermia applicator system allows adaptive treatment planning: Preliminary clinical results in tumour-bearing animals.

Hyperthermia (HT) as an adjuvant to radiation therapy (RT) is a multimodality treatment method to enhance therapeutic efficacy in different tumours. High demands are placed on the hardware and treatment planning software to guarantee adequately planned and applied HT treatments. The aim of this prospective study was to determine the effectiveness and safety of the novel HT system in tumour-bearing dogs and cats in terms of local response and toxicity as well as to compare planned with actual achieved data during heating. A novel applicator with a flexible number of elements and integrated closed-loop temperature feedback control system, and a tool for patient-specific treatment planning were used in a combined thermoradiotherapy protocol. Good agreement between predictions from planning and clinical outcome was found in 7 of 8 cases. Effective HT treatments were planned and verified with the novel system and provided improved quality of life in all but 1 patient. This individualized treatment planning and controlled heat exposure allows adaptive, flexible and safe HT treatments in palliatively treated animal patients.

A novel dual-wavelength laser stimulator to elicit transient and tonic nociceptive stimulation.

This study aimed to develop a new laser stimulator to elicit both transient and sustained heat stimulation with a dual-wavelength laser system as a tool for the investigation of both transient and tonic experimental models of pain. The laser stimulator used a 980-nm pulsed laser to generate transient heat stimulation and a 1940-nm continuous-wave (CW) laser to provide sustained heat stimulation. The laser with 980-nm wavelength can elicit transient pain with less thermal injury, while the 1940-nm CW laser can effectively stimulate both superficial and deep nociceptors to elicit tonic pain. A proportional integral-derivative (PID) temperature feedback control system was implemented to ensure constancy of temperature during heat stimulation. The performance of this stimulator was evaluated by in vitro and in vivo animal experiments. In vitro experiments on totally 120 specimens fresh pig skin included transient heat stimulation by 980-nm laser (1.5J, 10ms), sustained heat stimulation by 1940-nm laser (50-55°C temperature control mode or 1.5W, 5min continuous power supply), and the combination of transient/sustained heat stimulation by dual lasers (1.5J, 10ms, 980-nm pulse laser, and 1940-nm laser with 50-55°C temperature control mode). Hemoglobin brushing and wind-cooling methods were tested to find better stimulation model. A classic tail-flick latency (TFL) experiment with 20 Wistar rats was used to evaluate the in vivo efficacy of transient and tonic pain stimulation with 15J, 100ms 980-nm single laser pulse, and 1.5W constant 1940-nm laser power. Ideal stimulation parameters to generate transient pain were found to be a 26.6°C peak temperature rise and 0.67s pain duration. In our model of tonic pain, 5min of tonic stimulation produced a temperature change of 53.7±1.3°C with 1.6±0.2% variation. When the transient and tonic stimulation protocols were combined, no significant difference was observed depending on the order of stimuli. Obvious tail-flick movements were observed. The TFL value of transient pain was 3.0±0.8s, and it was 4.4±1.8s for tonic pain stimulation. This study shows that our novel design can provide effective stimulation of transient pain and stable tonic pain. Furthermore, it can also provide a reliable combination of transient and consistent stimulations for basic studies of pain perception.

Feedback Control System of Wafer Temperature for Advanced Plasma Processing and its Application to Organic Film Etching

A wafer temperature feedback control system during plasma processing with rapid, precise, and real-time temperature monitoring employing frequency-domain low-coherence interferometry was developed. To keep the temperature within a specific range, plasma was actively switched on and off, controlled by signals from a monitoring system. It was applied to an organic film etching process with an H2 and N2 mixture gas plasma. The organic material etching yield from atomic hydrogen has a relatively high sensitivity to temperature, and a constant temperature is required to achieve precise etching profiles. This system maintained the wafer temperature within a few degrees for H2/N2 plasma discharges. Duty ratios per discharge gradually decreased because the temperature of the chamber component parts around the wafer increased. The trench width etched in the organic film increased with increasing wafer temperature. This is because of a temperature dependence balance between the etching reaction and protection film formation on the trench sidewall.

Hemostasis Plug for an Electromagnetic Thermotherapy and Its Application for Liver Laceration.

Accident-induced liver trauma is a significant human health concern, as this organ is readily injured during periods at which the abdominal region is compromised. In this work, electromagnetic thermotherapy was successfully developed and employed in vitro and in vivo to treat livers that had been lacerated. Briefly, a new hemostasis plug was integrated with an electromagnetic thermotherapy system (ETS) to perform surgery on lacerated livers. The high-frequency, alternating electromagnetic field (EMF) was generated by the ETS and was shown to induce a pre-set temperature increase within the hemostasis plug embedded in the target tissue. In order to prevent overheating and maintain a constant hemostasis temperature, a temperature feedback control system was utilized. The effect of the intensity of the EMF on the heating capacity of the ETS-hemostasis system was first explored. Furthermore, the relationship between the coagulation zone and operating temperature were investigated in vitro. By utilizing the temperature feedback control system, the hemostasis plug could be heated to a specific temperature for efficient hemostasis. With this approach, the optimal treatment temperature and time were investigated for liver laceration. Lacerated livers from New Zealand white rabbits were successfully treated with the hemostasis plug and ETS within a short period of time. When compared with the traditional perihepatic packing approach, the volume of blood loss from liver laceration surgeries treated by ETS has been dramatically reduced by 83%, suggesting a high therapeutic potential for this system.

Dual-Row Needle Arrays Under an Electromagnetic Thermotherapy System for Bloodless Liver Resection Surgery

Electromagnetic thermotherapy has been extensively investigated recently and may become a new surgical modality for a variety of medical applications. It applies a high-frequency alternating magnetic field to heat up magnetic materials inserted within the human body to generate tissue coagulation or cell apoptosis. Using a new procedure with dual-row needle arrays under an electromagnetic thermotherapy system with a feedback temperature control system, this study demonstrates bloodless porcine liver resection, which is challenging using existing methods. In vitro experiments showed that hollowed, stainless-steel needles could be heated up to more than 300 °C within 30 s when centered under the induction coils of the electromagnetic thermotherapy system. In order to generate a wide ablation zone and to prevent the dual-row needle arrays from sticking to the tissue after heating, a constant temperature of 120 °C was applied using a specific treatment protocol. The temperature distribution in the porcine livers was also measured to explore the effective coagulation area. Liver resection was then performed in Lan-Yu pigs. Experimental results showed that seven pigs underwent liver resection without bleeding during surgery and no complications afterward. The dual-row needle arrays combined with the electromagnetic thermotherapy system are thus shown to be promising for bloodless tissue resection.

High-precision temperature control and stabilization using a cryocooler

We describe a method for precisely controlling temperature using a Gifford-McMahon (GM) cryocooler that involves inserting fiber-reinforced-plastic dampers into a conventional cryosystem. Temperature fluctuations in a GM cryocooler without a large heat bath or a stainless-steel damper at 4.2 K are typically of the order of 200 mK. It is particularly difficult to control the temperature of a GM cryocooler at low temperatures. The fiber-reinforced-plastic dampers enabled us to dramatically reduce temperature fluctuations at low temperatures. A standard deviation of the temperature fluctuations of 0.21 mK could be achieved when the temperature was controlled at 4.200 0 K using a feedback temperature control system with two heaters. Adding the dampers increased the minimum achievable temperature from 3.2 to 3.3 K. Precise temperature control between 4.200 0 and 300.000 K was attained using the GM cryocooler, and the standard deviation of the temperature fluctuations was less than 1.2 mK even at 300 K. This technique makes it possible to control and stabilize the temperature using a GM cryocooler.

Spatial and Temporal-Controlled Tissue Heating on a Modified Clinical Ultrasound Scanner for Generating Mild Hyperthermia in Tumors

A new system is presented for generating controlled tissue heating with a clinical ultrasound scanner, and initial in vitro and in vivo results are presented that demonstrate both transient and sustained heating in the mild-hyperthermia range of 37 ( degrees )C-42 ( degrees )C. The system consists of a Siemens Antares ultrasound scanner, a custom dual-frequency three-row transducer array and an external temperature feedback control system. The transducer has two outer rows that operate at 1.5 MHz for tissue heating and a center row that operates at 5 MHz for B-mode imaging to guide the therapy. We compare the field maps obtained using a hydrophone against calculations of the ultrasound beam based on monochromatic and linear assumptions. Using the finite-difference time-domain (FDTD) method, we compare predicted time-dependent thermal profiles to measured profiles for soy tofu as a tissue-mimicking phantom. In vitro results show differential heating of 6 ( degrees )C for chicken breast and tofu. In vivo tests of the system were performed on three mice bearing Met-1 tumors, which is a model of aggressive, metastatic, and highly vascular breast cancer. In superficially implanted tumors, we demonstrate controlled heating to 42 ( degrees )C. We show that the system is able to maintain the temperature to within 0.1 ( degrees )C of the desired temperature both in vitro and in vivo.

Force feedback temperature control for hot-tool plastic foam cutting

This paper presents the ideation of a force feedback temperature control system for advanced hot-tool plastic foam cutting systems. With respect to other controllers, the force feedback temperature control strategy is simple to apply given that it modulates the electrical power input independent of the predetermined tool path and feed rate. The control strategy is implemented by making a series of one-dimensional cuts with a hot wire. The electrical power input to the hot wire is modulated to provide constant tool temperature. Since the cutting force and kerf width are both dependent on the tool temperature, maintaining a constant tool temperature results in consistent cut surface characteristics. The force feedback temperature control theory and its practical implementation in one dimension are presented as well as an accurate description of the cutting process. Experimental results are presented to validate both theoretical assumptions and practical benefits. A number of barriers to implementation for three-dimensional sculpting are discussed with possible solutions. The experimental results validate the predictions that force feedback temperature control is an effective control method for hot-tool plastic foam cutting.

Localised heating of tumours utilising injectable magnetic nanoparticles for hyperthermia cancer therapy

This study reports an investigation of hyperthermia cancer therapy utilising an alternating magnetic field to induce a localised temperature increase on tumours by using injectable magnetic nanoparticles. In-vitro and in-vivo experiments represent the feasibility of hyperthermia cancer therapy. A feedback temperature control system was first developed to keep the nanoparticles at a constant temperature to prevent overheating in the tumours such that a safer and more precise cancer therapy becomes feasible. By using the feedback temperature control system, magnetic nanoparticles can be heated up to the specific constant temperatures, 37, 40, 42, 45, 46 and 47 degrees C, respectively, with a variation less than 0.2 degrees C. With this approach, the in-vitro survival rate of tumour cells at different temperatures can be systematically explored. It was experimentally found that the survival rate of cancer cells can be greatly reduced while CT-26 cancer cells were heated above 45 degrees C. Besides, localised temperatures increase as high as 59.5 degrees C can be successfully generated in rat livers by using the proposed method. Finally, complete regression of tumour was achieved. The developed method used injectable magnetic nanoparticles and may provide a promising approach for hyperthermia cancer therapy.

Development of temperature feedback control system for piezo-actuated display package

This paper describes a temperature management system for a deformable mirrors of piezo-actuated display package (PADP). This package which is integrated in microbeam projectors is used in portable devices such as cellphones, laptops, and personal digital assistants (PDAs), to name a few. Ambient temperature change is a critical factor affecting the performance of PADP. To reduce this effect of ambient temperature change, a temperature control system using a microheater and a temperature feedback circuit is developed. A computational model of the transient thermal analysis for the feedback control system is also developed. The obtained theoretical results are in a good agreement with the experimental measurements. Under this controlled system, the magnitude of the temperature fluctuation is reduced by ±0.5 °C. In order to enhance the performance of the developed system, various values of the temperature sensor resistance are used, leading to a reduction of about 10% of the temperature fluctuation.

Safety and performance of a novel intravascular catheter for induction and reversal of hypothermia in a porcine model.

This study was undertaken to assess the acute safety and feasibility of rapidly inducing, maintaining, then reversing hypothermia using a novel heat transfer catheter and a closed-loop automatic feedback temperature control system to overcome limitations imposed by current clinical practices used for perioperative cooling and warming. Six swine (mean mass, 53.8 +/- 3.6 kg) were studied. The heat transfer catheter was placed in the inferior vena cava via the femoral vein. Hypothermia to 32 degrees C was induced, maintained for 6 hours, then reversed to 36 degrees C. The time needed to induce and reverse hypothermia was recorded via continuous temperature monitoring of the lower esophagus, cerebrum, and rectum. Electrocardiography provided continuous monitoring, and blood draws were made at baseline and at 2-hour intervals. Examination of the catheter in situ was performed after the animals were killed. Cooling from 36.2 to 32.0 degrees C was rapid and uniform (mean, 7.3 +/- 0.7 degrees C/h), with animals reaching the target temperature within 60 minutes. Rewarming was also easily controlled, with animals' temperatures reaching 36 degrees C within 130 minutes. No arrhythmia was observed, and all hematological variables were within the normal range for swine. There was no evidence of hemolysis or platelet changes. Little to no thrombosis was observed. The data presented here suggest that rapid induction and reversal of hypothermia are technically possible using a core intravenous cooling catheter; this method would provide a safe, rapid, and exquisitely reproducible way to induce hypothermia with subsequent restoration of normothermia.

Safety and Performance of a Novel Intravascular Catheter for Induction and Reversal of Hypothermia in a Porcine Model

OBJECTIVE: This study was undertaken to assess the acute safety and feasibility of rapidly inducing, maintaining, then reversing hypothermia using a novel heat transfer catheter and a closed-loop automatic feedback temperature control system to overcome limitations imposed by current clinical practices used for perioperative cooling and warming. METHODS Six swine (mean mass, 53.8 ± 3.6 kg) were studied. The heat transfer catheter was placed in the inferior vena cava via the femoral vein. Hypothermia to 32°C was induced, maintained for 6 hours, then reversed to 36°C. The time needed to induce and reverse hypothermia was recorded via continuous temperature monitoring of the lower esophagus, cerebrum, and rectum. Electrocardiography provided continuous monitoring, and blood draws were made at baseline and at 2-hour intervals. Examination of the catheter in situ was performed after the animals were killed. RESULTS Cooling from 36.2 to 32.0°C was rapid and uniform (mean, 7.3 ± 0.7°C/h), with animals reaching the target temperature within 60 minutes. Rewarming was also easily controlled, with animals’ temperatures reaching 36°C within 130 minutes. No arrhythmia was observed, and all hematological variables were within the normal range for swine. There was no evidence of hemolysis or platelet changes. Little to no thrombosis was observed. CONCLUSION The data presented here suggest that rapid induction and reversal of hypothermia are technically possible using a core intravenous cooling catheter; this method would provide a safe, rapid, and exquisitely reproducible way to induce hypothermia with subsequent restoration of normothermia.

Control system for an MRI compatible intracavitary ultrasound array for thermal treatment of prostate disease.

A 16-channel ultrasound intracavitary array is currently being used in a clinical setting for localized hyperthermia treatment of prostate tumours. Currently, the individual power to each array element is adjusted based on the clinician's judgement of the temperature measured at the locations of invasive thermocouple probes. MRI-derived temperature measurements may be useful for a feedback control system that non-invasively regulates the temperature distribution by adjusting the power to the elements of the array. MRI has been shown to provide accurate, high resolution, non-invasive thermometry. A proportional-plus-integral, single-input, single-output controller was designed to evaluate the feasibility of MRI-derived temperature feedback with this applicator. Input parameters for the controller were determined by modelling the tissue response to the heating from the array. Ex vivo and in vivo experiments evaluated the ability of the MRI-based temperature feedback control system to achieve and maintain a target temperature for a sustained period similar to that of a clinical hyperthermia treatment. With the controller set to a reference temperature of 43 degrees C and a rise time of 6 min, the temperatures within the ex vivo tissue (n = 6) were 43.1 +/- 0.3 degrees C after reaching the reference temperature and had a rise time of 9.5 +/- 0.3 min. In vivo results using rabbit thigh muscle (n = 7) showed that the steady state temperatures were within +/- 1 degree C of their target temperatures. These results demonstrated the feasibility of a temperature feedback for controlling the heating from an intracavitary transrectal array based on temperature information from MR images.

Control system for an MRI compatible intracavitary ultrasound array for thermal treatment of prostate disease

A 16-channel ultrasound intracavitary array is currently being used in a clinical setting for localized hyperthermia treatment of prostate tumours. Currently, the individual power to each array element is adjusted based on the clinician's judgement of the temperature measured at the locations of invasive thermocouple probes. MRI-derived temperature measurements may be useful for a feedback control system that non-invasively regulates the temperature distribution by adjusting the power to the elements of the array. MRI has been shown to provide accurate, high resolution, non-invasive thermometry. A proportional-plus-integral, single-input, single-output controller was designed to evaluate the feasibility of MRI-derived temperature feedback with this applicator. Input parameters for the controller were determined by modelling the tissue response to the heating from the array. Ex vivo and in vivo experiments evaluated the ability of the MRI-based temperature feedback control system to achieve and maintain a target temperature for a sustained period similar to that of a clinical hyperthermia treatment. With the controller set to a reference temperature of 43°C and a rise time of 6min, the temperatures within the ex vivo tissue (n

Biophysical characteristics of radiofrequency lesion formation in vivo: Dynamics of catheter tip–tissue contact evaluated by intracardiac echocardiography

During clinical radiofrequency catheter ablation a wide range of delivered power may be necessary to achieve success despite an apparently stable catheter position on fluoroscopy. The purpose of this study was to use intracardiac echocardiography to characterize the relation between catheter tip–tissue contact and the efficiency of heating during applications of radiofrequency energy in vivo and to determine whether intracardiac echocardiography could be used prospectively to improve tissue contact. A closed-loop temperature feedback control system was used during radiofrequency applications at five anatomic regions in the right atrium of 15 anesthetized dogs to ensure achievement of a predetermined temperature (70° C) at the catheter tip thermistor by automatic adjustment of delivered power (maximum 100 W). The efficiency-of-heating index was defined as the ratio of steady-state temperature (degrees Celsius) to power (watts). Two-dimensional intracardiac echocardiography was used to evaluate movement of the catheter tip relative to the endocardium. Perpendicular contact was scored as good, average, or poor and lateral catheter sliding as <2, 2 to 5, or >5 mm. Two groups of animals were included: group 1, in which tissue contact was guided by fluoroscopic and electrographic criteria for stability of contact, with intracardiac echocardiography used simply to observe the application; and group 2, in which tissue contact was guided by intracardiac echocardiography. Of 66 applications, 18 (27.3%) had poor perpendicular contact on echocardiography, and 12 (18.2%) demonstrated lateral sliding of >5 mm even though they had been considered to have good tissue contact by fluoroscopic and electrographic criteria. Perpendicular catheter contact and anatomic location were shown to be independently related to the efficiency-of-heating index. Applications with good perpendicular contact had a significantly higher efficiency-of-heating index and a significantly greater lesion size than those with average or poor contact. The percentage of applications having good perpendicular tissue contact and the lesion size were significantly greater when tissue contact was guided by intracardiac echocardiography compared with fluoroscopic and electrographic guidance. This study demonstrates that variations in catheter tip–tissue contact account for differences in the efficiency of tissue heating, independently of the anatomic site of the application. Poor tissue contact was observed by intracardiac echocardiography and confirmed by indexes of tissue heating in approximately one third of radiofrequency applications despite a fluoroscopic appearance and electrographic morphologic appearance suggestive of good tissue contact. There was a significant correlation between echocardiographic evaluation of tissue contact, parameters of tissue heating (efficiency-of-heating index), and lesion size. In addition, intracardiac echocardiography could be used prospectively to improve the percentage of good contact applications and increase the lesion size. (Am Heart J 1997;133:8-18.)

Multipoint temperature control during hyperthermia treatments: theory and simulation.

A real-time multipoint feedback temperature control system has been designed and implemented with an ultrasound phased-array applicator for hyperthermia. The control parameters are the total power available from the supply and the dwell times at a sequence of preselected heating patterns. Thermocouple measurements are assumed for temperature feedback. The spatial operator linking available heating patterns to temperature measurements is measured at the outset of the treatment and can be remeasured on line an adaptive implementation. A significant advantage of this approach is that the controller does not require a priori knowledge of either the placement of the thermocouples or the power distribution of the ultrasound heating patterns. Furthermore, the control loop uses a proportional integral (PI) gain in conjunction with a singular value decomposition (SVD) of the spatial transfer operator. This approach is advantageous for robust implementation and is shown to properly balance the power applied to the individual patterns. The controller also deals with saturation in the inputs without integrator windup and, therefore, without temperature overshoot. In this paper, we present the theoretical formulation and representative simulation results of the proposed controller. The control algorithm has been verified experimentally, both in vitro and in vivo. A subsequent paper describing these results and the practical implementation of the controller will follow.