Hardware will be developed for both assistive and surgical robotics platforms.

• The assistive robotics platform will be able to model common environments and assist humans in manipulation tasks
  • Purchased hardware will include robot arms, hands, and sensors. Major pieces of equipment purchased to date are:
    • The Barrett WAM Arm
    • The Schunk Anthropomorphic Hand (pdf)
    • VICON MX 6-camera system
    • Pressure Profile Systems tactile sensors (see our tactile sensor simulator!)
    • A second WAM arm (planned)
    • A Barrett Hand (planned)
• The surgical robotics platform will focus on manipulating, sensing, and modeling deformable soft tissue using a modified version of the da Vinci surgical system.
  • Equipment includes:
    • Experimental custom system based on the da Vinci Classic
    • Clinical system (da Vinci S) on loan
    • An ultrasound machine
    • An eye tracking system

Our software and mechatronic infrastructure must be applicable to many different types of hardware systems. We propose to construct two robotic platforms, with different sensing, modeling, and manipulation requirements, in order to guide development and ensure generality. The hardware will include a set of off-the-shelf components (some already owned and some to be purchased), including robot arms, artificial hands, tactile sensors, vision and imaging sensors, position trackers, and human input devices. A significant portion of the development work is to integrate these components along with the software and mechatronic infrastructure into two functional experimental platforms for robotics research. We emphasize that, although there are significant purchases required to create these platforms, this a developmental activity. These components cannot simply be assembled into a working system. Rather, they will be generically interfaced through the software infrastructure. Also, for some manipulation components, the mechatronic interfaces described are needed to control the system. The two experimental platforms we will develop and the primary purchases we will make are described below.

Assistive Robotics

Surgical Robotics

Two “Human-in-the-loop” teleoperated surgical robotic systems are involved in this project. The first is a custom system with imaging and vision sensors that can acquire patient-specific deformable tissue models. The sensors will include a stereo endoscope, video cameras, ultrasound scanner, and force sensors on surgical tools. The models will focus on deformable soft tissues that can be tracked using computer vision techniques and whose mechanical properties can be acquired using force and motion sensing. The manipulation system includes of two da Vinci master manipulators, “classic” patient-side manipulators with surgical tools, and 3-D visualization for the operator.  In addition, a da Vinci S system is on loan from Intuitive Surgical, Inc. This is a clinical version of the robot being used in the JHU Swirnow Mock Operating Room for systems integration experiments, in a realistic mock clinical setting.

Mechatronic interfaces exist between the control software and the sensors and actuators that interact with the physical world.

We have designed a new controller using IEEE 1394 (Firewire) for communications. This controller consists of two boards: an IEEE-1394 FPGA Controller and a Quad Linear Amplifier. Key features of this controller are:

• Provides equivalent functionality to Low Power Motor Controller (LoPoMoCo), which is a custom board with an ISA bus interface developed in 2004
• Uses FPGA to provide bridge between IEEE 1394 bus and I/O hardware
• All control software implemented on host PC (no embedded software development required)
• Includes linear power amplifiers in bridge configuration, providing bidirectional motor control using a single power supply
• Enables closed-loop control up to 8 kHz
• FPGA has sufficient capacity for additional functionality, including microprocessor
• More detailed specifications available here.

All design files are available in the public SVN repository, with a Trac interface that includes a wiki for documentation:

• Documentation for mechatronics
• git repository for mechatronics

The git repositories include the schematic and PCB design files (Altium Designer format) and the FPGA (Verilog) source code.

The cost of one 4-axis board set (one FPGA and one QLA) is about $1,150, assuming a total run of at least 40 board sets. The price will decrease with larger quantities.

See Design Review 1 presentation (pdf) for an early design review; the resulting design decisions and user requirements are summarized below:

For the experimental platforms being developed, most of the sensors and actuators will be provided by purchased subsystems. Just as open software interfaces are fundamental research enablers, it is crucial to have open mechatronic interfaces.Several years ago, we created a custom Low Power Motor Controller (LoPoMoCo) to support our research (see figure). This board was originally designed to drive a small snake-like robot developed for throat surgery, but was subsequently applied to other robotic systems A custom solution was created because there were no commercially-available boards that satisfied the requirements to perform voltage (speed) or current (torque) control of DC motors, enforce torque limits in hardware (even when configured for voltage control), and provide precise feedback of small motor currents (100 mA and lower).The LoPoMoCo is a half-length ISA board that provides all I/O and power amplification for 4 robot axes. Although this board satisfied our control requirements, we noted a few areas for improvement, such as the interface to the control computer. The main problem is that a board physically located inside the PC (whether ISA or PCI) requires a significant amount of cabling to the remote sensors and actuators. One solution is to create a distributed system with embedded microprocessors located near the sensors and actuators. For research, however, we prefer to implement all control on the PC because it provides a low-cost, high-performance processor and a familiar development environment. Thus, we are creating a new robot controller that uses IEEE 1394 (Firewire), rather than ISA or PCI, to communicate between the PC and the remote I/O hardware. A key feature of this controller is that the remote hardware uses an FPGA to provide the interface between the Firewire and the I/O devices; there is no remote microprocessor and therefore no additional overhead. This design will enable closed-loop control to be performed on the PC at frequencies of 8 kHz and higher, assuming a real-time operating system is employed.